Sometimes you have to use brute force. I'm assuming you have heavy iron
pipes in the wall, due to having a metal pipe leading into it. The
thing you need is any movement even if it is inward. A smack with a
hammer might accomplish this, if it moves at all, at least it isn't
stuck anymore, give it a twist with a pipe wrench. If all that fails, a
cold chisel deftly operated could take a slice out of it then you could
collapse it in. I'd even consider a metal cutting blade in a sawzall.
The outer pipe (again, assuming it is something like 1 1/2" galvanized)
can take a lot of abuse and the inside isn't required to be smooth to
seal the new pipe, just don't make the threads unusable. I'm not
advising going after it with a sledge hammer, but a 2lb hammer at less
than full force is a lot of persuasion.