Crash,
May I offer a bit of Bible Teaching here. You seem to accept that it is good to know what the book says, whatever your choice of beliefs.
Matt 5:22 is careful to refer to brothers. "Whoever says to his brother, 'You fool!'" It's okay to call non-brothers, unbelievers, fools. And even to hate them. "I hate those who hate God, with a perfect hatred." Ps 139:21-22.
Also, Yeshua (Jesus) taught that there would be phoney and real "Christians" (believers). He called the first tares, referring to their comparison as a certain kind of weed, that grows with wheat. The wheat, when full, tends to be bowed over with the weight of the full seed-heads. The tares, otherwise identical, have tiny seeds, and sit up all perky and proud. Latter on, He commented that you would know the true believers by their love for one another, not their love for you. If you mess with one of them, you can expect the most severe response, because people who really love one another stand up for one another. They ought to forgive you for hurting them, but not for hurting one of their own, and especially not for hurting God.
So, in case you might ever want to be a part of God's family, you do well to study how to tell the real thing from the counterfeits.
Cheers,
Stephen