Lenny Dykstra -- Fires Back at Mickey Rourke ... You're a Disgrace to the Facelift Industry (VIDEO)

More trash talk from Lenny Dykstra -- who says Mickey Rourke is so ugly, he "set the whole facelift industry back 10 years."

The ex-MLB star -- who's now a NY Times bestselling author -- is in an epic war with Rourke ... after recently telling Howard Stern the actor still owes him $30k and insinuated it was for coke.

Rourke called BS on Dykstra's story -- and said he'd "rip him a new f****** asshole" if he ever saw him again.

Now Dykstra's firing back -- insulting Mickey's face, his age ... and joking that he'd beat Mickey's ass first.

So ... settle this in the ring???