Why is homeschooling safer?

There's no answer because there's no long term evidence either way. It's probably not. Even if you could statistically show homeschooling was somehow safer, I would assume that any correlation is intimately tied to the distribution of those home-schooled vs those public schooled. This would be heavily weighted to wealth, and therefore better neighborhoods (due to socioeconomic status). By extension, everything would be safer and you could no more say that homeschooling is safer than being in an affluent neighborhood is safer.

Additionally, even if everything I said could be disproven, the temporal characteristics need to be taken into consideration and social behaviors of those home-schooled vs. private schooled vs. public schooled would need to be correlated. For example, is there any regression in terms of violence that can NOT be attributed to socioeconomic status when comparing home-schooled students against public-schooled students at 40 years old (aka, did homeschooled students learn the social lessons necessary to successfully navigate the world when compared to another sample).

Safer? To say that I doubt it is an understatement. Different? Most certainly. Is this question actually answerable even remotely? No.