That's a harsh way of putting it, but... yes. Longsuffering, lightheartenedness, forgiveness, and stoicism are all virtues.
What possible benefit is there in taking offense when no offense is intended? Why wouldn't we want to steer people away from being offended rather than steering them towards it?
Firstly, I'd tell anybody who's offended by a dated black caricature not to be offended unless they're certain the artist intended offense.
Secondly, in an instance where individual X draws such a caricature and individual Y is sufficiently offended by it to want to say something, no training is required on the part of either X or Y for Y to take X aside and say "Many black people consider these dated caricatures offensive because...". X can then accept the advice or reject it. If he accepts it, problem solved. If he rejects it, diversity training wasn't going to fix the problem anyway.
If diversity training is nothing more than an explanation of some of the things various groups may find offensive, I suppose there's no harm in it. But what if it's a vector for political activism? What if it's used to inject guilt, contempt, divisiveness, or a malcontented, unforgiving attitude into the learners? Then it becomes a harm. I'm sure that's what everyone here is worried about.