Ignorance coupled with Zealousness. Ignorance breeds fear and hate that escalates to horrendous deed. Zealousness makes man an unthinking animal. God gave us brain and it would be an insult to HIM if we do not use it.

Some words start with Z and have double S:

zaniness. zestfulness. zealousness. zipless. zoneless. zestless.

An abstract noun that starts with Z is zeal, a word for great energy or enthusiasm in pursuit of a cause or an objective.

According to Webster's dictionary, zealousness is "marked by fervent partisanship", thus an appropriate sentence might be: "Joe McCarthy zealously denounced the speaker as being a traitor, merely because of his opposing political beliefs."