I don't think it's rude, but I do undertand that your feeling upset about it. It's natural not to want je birth of your first child to be overshadowed, and at the rusk of making sweeping generalizations I'm guessing your dh is from a close family?

I was (irrationally) angry at two of my cousins for daring to be pregnant and due 2 months after my EDD with my first. But you need to step back and look at it from their pov

From their side it's all about them, not about you. It's not like they have chosen the date deliberately, is it?
If you seriously think it's intentional the that's another matter entirely, but
If he's from a large family it's possibly about logistics as much as anything else, as others have said.