I see nothing wrong with Mickey still being copyrighted. Disney actually uses that patent, and still does, voluminously so, so it isn't like society is being shortchanged or whatnot. That being said in general I think a further 20 year extension would not be a good idea and some more measured approach would be preferable for sure.
Just because Disney still uses it doesn't mean they should be able to take it out on the rest of us.
Just because Disney has been using Mickey for a long time doesn't mean that they should lose the copyright. I think whether something is actually being used should matter. Also, Mickey does belong to Disney, and they've used Mickey a lot. I don't see how it makes sense equating Disney getting money for Mickey's use as somehow robbing the rest of us.