I think Delap saw the ball laying against SWP and thought a could hard kick would finish the job. Ref right to send him off. If he didn't see SWP's kick then he can't send him off.
I thought the West Brom sending off was harsh. Both players appeared to be going for a 50/50 ball. Mind you, with Carson in goal it wouldn't have made a difference. West Brom look they really can't be a*sed.