I'm not a fan of fighting over the blinds with a pair of 4s, but whatever. I assume you expect him to fold a better hand here on the river? Given the way he's played it, how likely is that? Is he going to buy that you had 56, say, and picked up trips on the river?

There is one other potential problem, too. It's vaguely possible villain is a fan of another forum, and is playing his favorite hand again. If he cross-posts here and knows who you are he's undoubtedly getting an enormous chuckle right about now.