WFAN's Gregg Giannotti fires back at 'insecure bully' Mike Francesa

The impersonations will not cease.

WFAN morning show co-host Gregg Giannotti fired back at Mike Francesa on Thursday after the big guy lambasted him, his on-air schtick and the "Boomer and Gio" program on Wednesday.

"He's an insecure bully who thinks those things are going to affect me, affect us, and it just doesn't," Giannotti said, adding that "it's radio," he doesn't care when he's mocked because he and co-host Boomer Esiason do it too and that he was "laughing at it, more than anything else" when informed of Francesa's ripjob.

Francesa blindsided Giannotti, saying he was "short on ability" and that his show "stinks" after, Francesa claimed, he listened to the show for an hour Wednesday…