YOU'RE WRONG ... so says fellow short guy Doug Flutie, who's telling TMZ Sports he's living proof that the vertically challenged can THRIVE in the pros!

Flutie is 5'10" -- which is a good height among normies but short by NFL quarterback standards.

Murray is also 5'10" -- and the knock on the Heisman Trophy winner is that he just doesn't have the height to make the tough throws over those gigantic NFL linemen.

Enter Flutie, who's really going to bat for Murray ... explaining, "The biggest problem with a lot of short quarterbacks is they don't have the arm strength. [Murray] does. He can make all the throws."

Flutie also says the implementation of spread offenses throughout the NFL will help Murray find passing lanes ... and says it shouldn't be hard for him to replicate the success he had at Oklahoma.

"He can throw from all kinds of angles. We see that with [Patrick] Mahomes and you'll have the same thing with Kyler Murray."