Being told your opinions are problematic and hurtful is part of the process of changing them. This is the "paradox of intolerance", without a certain degree of intolerance of unacceptable beliefs, intolerance itself spreads further.

It is really the same process as having any ingrained belief challenged, it is going to make that person uncomfortable because something they took on faith is being challenged. That doesn't mean it's not something that should happen.