The best way to handle this--if you care to bother--is to keep good records of the stupid things he says. Then, if the Bills have a great season, you can own him with his own words. If you call him on it now, you risk looking silly if the Bills don't keep up this good play.
At the same time, I don't mind it when people diss the Bills generally, but I do mind when they do it when they lack any knowledge on the subject. Any of the detractors of the Bills who actually watched the 2 games have come out saying that the Bills are much better than they thought. The lazy commentators who are just repeating the meme that Bills Bad, Dolphins Good have put so much faith in it that they just can't accept that they were wrong since they didn't even see the game and assume that the Dolphins just haven't been playing up to their talent.
I stop listening to sports talk for the most part, but especially to this guy. He has "instincts" which means that he gets a small piece of information and then runs with some overly generalized rant with little support. Any further information he has on the subject he just spins as supporting his original, ill-informed theory.