I can't win...

I disengaged and was asked to please re-engage.
fDH is understanding to be more patient as SD12 and I are not bonding. It has been two years. I have been friendly and polite, but to the extent I would be to anyone in my home. Nothing extra anymore. It makes me too anxious and she doesn't welcome it. BUT, I love fDH, so I will try my best.

A few days ago, I was online and saw a few classes I thought would be interesting for SD. Her BM is the type to go roam the mall all of the time.

One of the courses is something she loves, but the other is something she hasn't really shown any interest in. (it's one class- 3hrs long-something different) DH was neutral about it, and actually got defensive about the second class, because "just because we put her in class, doesn't mean she'll start doing it." His tone was so defensive it actually surprised me and I just got up and left the room after saying "it was just a suggestion and moving forward I won't do it."

Snaggletooth doesn't drive or work, so all of this stuff falls on him, I was trying to help. Was I overstepping? Why is this such a trigger for him? I'm starting to realize that since he now knows my reluctance regarding his daughter, everything about her makes him defensive... I'm not sure how to approach this without starting another argument... Or do I just stick to my guns and remain somewhat disengaged?