If a healer gets too caught up in their DPS and fails to spot when heals are needed, then it's a problem. If a healer uses up all their MP on DPS, and is then unable to heal when it's needed, that's a problem. But it doesn't sound like either of those were the case. So long as you make sure you can keep up with the healing, anything else you can throw into damage is an overall boost to the group as a whole.

My best guess would be that the bard you were with had probably been in a previous run where the healer concentrated too much attention on their DPS and let it distract them from healing. It was still pretty idiotic of him/her to overgeneralize it that way, though. The problem wasn't a healer who used DPS attacks, it was a healer who failed to put enough of their attention into healing. Getting mad at you when you were balancing the two correctly was just stupid.