For heaven's sake, they're DESIGNED to be pushed shut. If they weren't, giving it a little nudge wouldn't be detected (and you'd have to force it all the way home, or rather you wouldn't and the manual would say don't do that, push the button). So go ahead, push it, that's what it's supposed to do. Will it cause damage? Duh, yeah -- about as much as pressing the button to close it, or playing a CD in the drive will. It's called wear and tear. You can't avoid it.
Hey, if you use the button too much, you'll probably end up wearing it out, then how will you open the drive? :^)