How do I remove this drain pipe from my garbage disposal?
That should be a slip fit and simply pull out.
It's possible that some prior worker glued the joint between 1&amp;2 with 3 inserted, and it got stuck that way. It's also possible that it's merely stuck with years of crud. In either case, it should pull out, twisting it while pulling may help to break whatever is sticking it loose, and if it just won't go you need a whole new set of parts 1, 2, &amp; 3