It's not paranoia, look at this thread alone and the responses from @xigoi , even on HN which is heavily moderated and leans to more liberal views. Terrible people are plenty. I'd think after the past few elections in the US that was obvious. Violence isn't the only reason to be cautions with strangers, mistreatment is another reason, having a negative interaction in general is unpleasant.

The solution is not to pretend people's experiences are invalid, or that somehow reducing the risk of harm is wrong, but to find ways to adapt, and be prepared to handle or dismiss negative interactions, as well as value the benefits of positive ones.