You can turn off iMessage by going to the Messages tab in settings and simply sliding the iMessage button to "off". However, I don't think that has any effect on the icon. I believe Apple treats it like the other built-in "important" apps on the front home screen: You can move it if you like, but you can never delete it.
I seem to recall reading about some people who never use certain built-in apps who just dumped all those icons into a single folder and then dragged that all the way to the end of the last page of icons....
