Because Jehovah God, the Almighty, the Creator of mankind; tells Christians in the Bible that it might; for good reasons, be necessary.
This is not an unusual practice. Everyone practices it in some form.
For example:
- Some families may tell their son or daughter: "I don't want you playing with Johnny any more." This is a form of curtailing fellowship. And no doubt they have good reasons.
- Some American Indian tribes practice 'banishment'. They have good reasons.
- Even most countries, arrest criminals; and place them in prison. This is a form of disfellowshipping. Their loved ones, their marriage mate, their children; are restricted from fellowship with them. Perhaps only a few times a year, and only for an hour or so; and that may be through a glass window with a phone for voice connection. This is an acceptable practice.
Responding to accusations of Cruelty:
Jehovah's Witnesses don't do quite as harsh as 'banishment' and 'prison'. No one is banished from being in our presence and singing with us. They can come to our meetings; they can sing; they can say 'amen'; they can walk up to the literature counter and receive for free any piece of literature for themselves (and their children, if they have.) They also are admitted to our 3-day conventions in large stadiums, for free. Upon request they can even receive personalized spiritual counseling from the elders. This does happen quite often. They end up being comforted, and strengthened spiritually, and emotionally.
I know of many human kindnesses done for disfellowshipped ones locally by elders and others; (including purchasing a vehicle for one lady; after having repaired her old one without cost to her; among other things. The lady has now disappeared and has not requested reinstatement for 5 years since then.)
We also accept pleas for reinstatement. They are not permanently banished. When disfellowshipped ones are willing to live by Jehovah's righteous requirements, they may make a plea for reinstatement. There is no time-limit with us, as in a prison sentence. We have helped so many find their way back again. And once they're back, they often mention that the action taken on them, was what helped jolt them to their senses and straighten up.
All the clamoring and bellyaching of 'apostates'; and other 'mainstreamers'; are embellished exaggerations; which we dismiss faster than they can finish their sentence.
Grounds for disfellowshipping, with references,
Adultery (sexual intercourse with a person other than your marriage mate), includes;
Abandoning wife and eloping with another woman - w79 11/15 31-2, w76 p.728
Planned adultery to break Scriptural marriage ties - w83 3/15 p.29
Remarriage without Scriptural permission - w56 10/1 p.597
Polygamy - jv 176
Dating a person not legally divorced - ks91-E p.135
Apostasy - w83 4/1 pp.22-4, km 8/80 pp.1, 4. includes;
Rebellion against Jehovahs organization - w63 7/1
Promoting sects - it-2 886
Associating with disfellowshipped people including;
Friends - ks91-E p.103, w81 9/15 pp.25-6, w55 10/1 p.607
Family - ks91-E p.103
Blood and blood transfusions - w61 1/15 ks91-E p.95, jv p.183-4
Drug use - ks91-E p.96
Drunkenness - ks91-E p.95, it-1 656
Dishonest business practices - w63 7/1, w86 11/15 14
Employment violating Christian principles - km 9/76 p.6, km 2/74
Working for any religious organization - ks91-E p.95
Working in a gambling institution - ks91-E p.136
Selling tobacco - ks91-E p.96
Contract work at a military establishment
False worship. Includes;
Attending another church ks91-E p.94
Following mourning customs that involve false worship - w85 4/15 p.25
Fornication it-1 863
Bestiality - w83 6/1 p.25
Incestuous marriage - w78 3/15 p.26
Artificial insemination and surrogate motherhood.
"True Christians, therefore, avoid surrogate motherhood as well as any procedures that involve the use of donated sperm, eggs, or embryos" g04 9/22;
"Artificial insemination of a married woman by a donor other than her husband makes her guilty of adultery" g74 8/8 p.28
sexual abuse of children - g93 10/8 p.10Reviling - ks91-E p.94, w96 7/15 pp.17-18; it-1 p.991; it-2 p.802
Fraud - ks91-E p.94, om pp.142-3
Gambling or related employment - w80 9/1, ks91-E p.136
Gluttony - w86 5/1
Greediness, this in used to include;
gambling ks91-E p.95
extortion ks91-E p.95, w89 1/15 22, it-1 p.789
greed in relation to bride-price: w98 9/15 p.25
Homosexuality - w83 6/1 pp.24-6
Idolatry - w52 3/1 p.138
Loose conduct - ks91-E pp.93, 96, w83 3/15 p.31, w73 9/15 p.574, it-2 p.264, ks91-E p.93, w83 3/15 p.31, w73 9/15 pp.574-6, w97 9/1 p.14, it-2 p.246.
This includes;
Sexual perversion
Disregard for Jehovah's moral standards
Disrespect, disregard or even contempt for standards, laws and authority,
Rather than restricted to the usual definition of sexual perversion, the Watchtower defines "loose conduct" as including "disrespect to elders". This enables this term to be used to disfellowship for a wide range of offences not elsewhere covered, and as such is used to cover all manner of sins, such as refusal to cease fellowship with disfellowshipped people, or even being contemptuous in a judicial meeting where no other sin can be proven.
Lying - ks91-E p.94, g00 2/8 p.21
Non neutral activities (involvement in politics and the military) - ks91-E p.96
Military service and non military service including working casual work (certain civilian work has recently been made a conscience matter w96 5/1 p.20) - ks91-E p.96
Obscene speech - ks91-E p.95
Parents condoning immorality - w56 p.566
Political involvement, including voting or holding a political card in Malawi - ks91-E p.96 (w99 11/1 p.28 made voting a conscience matter)
Porneia. Includes oral and anal sex between married couples, mutual masturbation between persons not married to each other, homosexuality, lesbianism, fornication, adultery, incest, and bestiality. - ks91-E p.93
Slander - ks91-E p.94, w63 7/1, w89 10/15 p.14, om p.142
Smoking or selling tobacco - km 2/74, ks91-E p.96
Spiritism (includes yoga w02 8/1 p.22) - w55 10/1 p.607
Stealing, thievery - om pp.142-5, ks91-E p.94
Subversive activity - w95 10/1 p.31
Uncleanness
Sexually perverse practices within marriage, such as oral and anal sex - w83 3/15 p.31
Heavy petting and breast fondling - ks91-E p.92
Touching of sexual parts - ks91-E p.91
Practice of viewing abhorrent Pornography - w2012 3/15 p.31
Violation of secular law if flagrant attitude - w86 10/1 p.31
Violence, extreme physical abuse, fits of anger - ks91-E p.96, w75 p.287, g01 11/8 p.12
Includes Boxing w81 7/1 pp.30-1, ks91-E p.142
Wilful non support of family, endangerment of mates spirituality - w88 11/1 pp.22-3, km 9/73 p.8, ks91-E p.95
Worldly celebrations such as Christmas - ks91-E p.95 (It appears celebrating birthdays is not a reason to be disfellowshipped)