This thread is beyond retarded. Every LW is somehow "undersized". Including Sherk, who happens to be a HUGE LW if short... the guy fought at WW and dominated until he fought GSP. Or Maynard, again a compact but big LW. Maybe you expect to find Brock Lesnar at LW? It's called LIGHTweight for a reason.
If anything, the UFC has the biggest lightweights in the world. Guys like Aoki are so skinny they'd get outmuscled by the smallest LW in the UFC if it wasn't for their subs. I would wager Aoki would get his ass handed to him by Sherk, let alone BJ. Hansen is also a mediocre LW with a patchy record who would get murdered by the UFC elite.
BJ has dominated tons of top 10 LWs at the peak of their career like it was nothing. Including Gomi, Uno, Duane Ludwig, Sherk, Joe Daddy, Florian and now Sanchez. Overrated he is not.