I went through the same crap about a year after coming back from Vietnam. Got up in the middle of the sermon (delivered by a radical who went on to high office in the California church, and who died recently) and walked right down the main aisle and out. Pissed my wife and in-laws off, but so what.
Besides, most priests, if you scratch their skins, are Marxists.
What a shame. What they should have done was to commit to daily prayer for his soul, go to their bishop and inform him and then head to a parish that is grounded in authentic Teaching and spirituality.
That's really too bad. It's scandalous, and in dioceses I've been in, pretty rare—it afflicts mostly the parishes of the very rich and the very poor. He could have found a different parish. But in my experience, friends who have left the Church over a solvable problem like that usually have had a few other problems they find less solvable, such as that they don't accept the Church's teaching on chastity or divorce and re-marriage.