If people gave actual good argumentation that wasn't irrelevant to the discussion at hand and not full of idiotic bias, maybe I would actually give a crap to what the blazers like you think.
Let's see, major beefs:
-"He's Mario, we don't need another Mario when there are other characters available to be the 5th Mario character."
Solution: Make Dr. Mario represent the Dr. Mario series since it is apparently another canon entirely.
-"He's a clone."
Solution: Make him semi-cloned. Not that hard to do unless you don't have brains.
-"Two Marios should not be on the CSS."
Solution: Make him an alternate selection to Mario like how Dragon Ball Z Budokai treats Teen Gohan and Great Saiyaman.
-"He has no place because *insert meaningless explanation*."
Counterargument: Neither does *insert character* because *insert meaningless explanation*.
-"But *insert character* has their place because *insert meaningless explanation*."
Counterargument: Dr. Mario has his place because *insert meaningless explanation*.
-"He won't be different. I know this as fact."
Solution: Get off the blaze or show me your time machine that proves this as absolute fact.
-"He can't be different."
Counterargument: He has elements from Dr. Mario yet to be used, he's a doctor, which means a doctor-based fighting style is an option, and he's a puzzle character of the "Nintendo Puzzle Collection", so he can reference other puzzle games such as Panel de Pon, Yoshi's Cookie, and even newer generation games like Brain Age or Big Brain Academy if need be.
-"That wouldn't be true to the source material."
Counterargument: Many of Smash's characters already go against source material.
-"BUT THAT'S FINE BECAUSE *insert meaningless explanation*."
Counterargument: Double standards. Doesn't help your argument in any way, shape, or form.
-"I don't like Dr. Mario, and I don't want him to return."
Counterargument: Ok. That is your opinion. I respect that.