TPM,
Are you serious that your son never hit a batter before college? Please believe me, I'm not doubting your word here, it just seems incredible to me.
Over the past 5 years, LL to current his current Babe Ruth including regular seasons and Fall Ball, my son has hit perhaps 10 batters among the several hundred that he has pitched to over that amount of time. You only have my word for it, but I believe unequivocally that he has never thrown at a batter on purpose. Still, he does try to use all of the plate and over that 5 year period he has made some location mistakes, occasionally on the inside.
My son has never acted proud of hitting anyone, in fact quite the opposite, but it is of interest to me how more experienced pitchers deal with the stress of unintentional HBs.
Actually, it sounds like even more stress to be pressured by your teammates into making a retaliation pitch, although the rationale for it seems to be pretty well understood and accepted as a necessary evil by all in the pro game.