I agree with @Strokethefurrywall, what do people actually get out of trying to make the OP feel trashy for doing things her way. Fair enough if she'd posted asking people's opinion on that, you have to expect some negative comments but she didn't. And the two aren't linked either, it's her dad ffs, no matter how naff he thought it was, he should want to be their for his daughter. Personally I declined a baby shower for my second and third baby as I feel it should be for first only if you even want one, but that didn't mean that when a friend invited me to hers, me and only a handful of others, mainly family, that I returned the invite with a 'Oh god how tacky and attention seeking you are' and refuse to attend, I mean seriously, what a bitchy thing to do/say.
I also disagree that others aren't interested in the gender because I am, if it's someone I care about. It's finding out a little bit more about the new little person you supposedly care about (and btw I didn't find out with my 3rd). At the end of the day the party is just an excuse to celebrate a long waited for child, if people can't see just a slimmer of positive in that no matter what your personal feelings on gender reveals then I find that sad .
And don't even get me started on the self righteous line of 'cake smashes are wrong when there are starving people' - I assume such people only ever eat to live, never have cake or wine or chocolate, you know food/drink that is purely consumed for enjoyment? With a cake smash the enjoyment is watching the child or the photos, with the pudding the enjoyment is purely the taste, it's still technically wasting food just getting different enjoyment from it. I did one myself, make a little cake for my daughter to eat herself. I didn't pay £100's of pounds for it but what people choose to spend their money on is their business. Some people may not like the pics I took but finally enough I didn't take it for them! Oh and dh and older kids are what was left of the cake anyway!
OP, back to the actually point of your thread, I think the only thing you did wrong was pander to him. I'd have just said 'good job it's not your decision then' and carried on talking about it how I wanted to. He sounds very childish and selfish trying to make this about him