The calling station who raises your turn bet has been slow-playing since the flop. He didn't just get there. He was already there and he finally couldn't wait anymore.

Why they do it

Calling stations who raise the turn have been sitting on a monster since at least the flop. They called the flop hoping you'd keep betting. When you did, they finally pulled the trigger. It's not a semi-bluff. It's the hand they've had all along finally coming out.

The adjustment

Fold everything except the nuts. You're not ahead. You were behind since the flop and you didn't know it. Just let it go.

What it's worth

Calling a turn raise from a calling station with two pair costs you the turn and river. That's $100-200 in losses that were completely avoidable. Believe the raise.