I can't get behind that - You're telling someone you won't support them because it's e

You're telling someone you won't support them because it's either too dumb, too weird, or just not your style. You're not even trying to be polite.

'I can't get behind that project. It's like building a house out of Legos and calling it a mansion.'

'I can't get behind that outfit. It looks like a sock went to prom.'

'I can't get behind that idea. It’s like trying to run a marathon in socks.'