[Andy B]

Your two pair is probably the "best" hand on fourth street. The problem is that, with four opponents, it is unlikely to be the best hand on the river. Someone is probably going to make a better hand, and meanwhile it is difficult for you to improve. It isn't the size of the pot so much as the size of the field.

Your opponent has played his hand exactly as many players would have if he had 86 in the hole. He might also have played rolled Sevens or pocket Fives this way. The fact of the matter remains that most players at this level will have two small pair crushed when they raise fifth street, regardless of the previous action or what's showing.