And at level 53, he/she spent enough time in dungeons to likely take repeated lashings for not DPSing. Generally speaking, a healer who keeps the group up while DPSing isn't going to catch much gripe from either camp of players who dislike healers DPSing, or those who get upset when they don't. The thing is, if you go into continuous DF instances, and you're adamant about not DPSing, you put yourself on a collision course to encounter these players at one point or another. It's an inevitable truth, I'm afraid.
It doesn't excuse the rotten behavior. Of course not. And healers who or new and/or new to an instance should be given a lot of breathing room. While it remains true that healer DPS is not required to clear content; it is also the cold hard truth that if you don't want to catch flack in PUGs, you have to play at a level that doesn't give anyone anything to complain about. For a healer, this does indeed mean that you DPS during your downtime, and also not tunnel vision the tank/group to an early grave.
Hopefully the OP has a change of heart, and can find a helpful FC with members willing to run content. It can be very satisfying weaving in offensive spells while healing. A new player should be as open-minded as they expect other people to be. It just allows for more enjoyment of the game.