It's too bad you had to blow up at him, OP.
I hope he finally got the point, at least. Being nagged to be more enthusiastic about something is just about the most sure-fire way to kill any
enthusiasm one might have had.
I've been thinking about this thread a lot. My mom loves to garden. I love that she
loves it. I don't love it myself. I show my support and enthusiasm in all the ways I can, like by listening to her talk about the garden and buying her stuff for the garden and taking pictures of her garden. But I'm not interested in helping her dig stuff or weed or water or anything like that. I try really, really hard to be enthusiastic about it in my way, and I think she
tries really, really hard not to push me in a direction I don't want to go. If either person is not aware of the need to maintain that balance, bad things can result.
On the one hand, I can see how your response in the dialogue you posted--depending on tone, body language, etc.--might not have struck him as sufficiently enthusiastic and encouraging--of his own enjoyment, if not of the thing itself. If my mom said, "I'm thinking of getting this new trellis for the garden! What do you think?" and I was just like, "Sounds great. Go get it. Blah." I think she might be kind of hurt. I would be more like, "Oh, that sounds awesome. It will go really well with the one you already have. Where are you going to put it?" BUT
--if there was a history of my mom whining about how I wasn't enthusiastic enough and trying to "force" me to be more interested, that would really, really decrease the level of effort I was willing to put into it. That's what I mean about it being a balance. If one person has already upset the balance by being too demanding, it's hard for the other person to figure out the best way to react. Maybe you guys need to start over with a clean slate about Halloween.