This may wind up being the most unexpected Twitter feud of 2012: Motley Crue bassist Nikki Sixx vs. Kirk Cameron, a.k.a. Mike Seaver from the '80s television show 'Growing Pains.' Sixx is one of a growing number of celebrities speaking out against Cameron's recent anti-gay marriage comments on 'Piers Morgan Tonight.'

"Kirk Cameron, a--hole of the week," Sixx tweeted on Sunday morning. On Friday, Morgan asked Cameron for his thoughts on gay marriage, and the active evangelist was honest.

"Marriage is almost as old as dirt, and it was defined in the garden between Adam and Eve," Cameron said. "One man, one woman for life till death do you part. So I would never attempt to try to redefine marriage. And I don't think anyone else should either."

He added that homosexuality is "unnatural" and "ultimately destructive to so many of the foundations of civilization." Sixx, like Cameron's 'Growing Pains' co-stars Tracey Gold and Alan Thicke, disagreed.

"I get the 'Freedom of speech' tweets from you guys," Sixx tweeted responding to his followers. "I just have a really hard time excepting people bashing gay marriage. Love Is Love." This is the second time in recent weeks Sixx has commented on 'Piers Morgan Tonight.' In February he took to Facebook to further explain his comments about enabling doctors that surround troubled celebrities.