"[Mesnick] was acting like an ass," Firestone -- who appeared as The Bachelor's third-season star in 2003 -- toldUs Weekly in a Friday report.
"I hope that Jason and that other girl are truly happy and all that other stuff. This might sound malicious but what a stupid thing to do. It's kind of a little depressing. This guy's a father, and you'd think he'd be kind of a stand-up guy. He does the whole thing, I certainly would never coach my son to be anything less than a gentleman. Just act like a gentleman!"
Firestone questioned why Mesnick made the decision to propose marriage to Rycroft during last November's Final Rose Ceremony taping only to later dump her on-air in favor of Malaney during January's taping of the season's After the Final Rose special.
"If he didn't have his mind made up, don't do anything," Firestone told Us. "Don't feel that you are so pressured into having to propose or make a decision. There's no reason that you have to do anything, especially if you're so torn that you're crying like a little girl on that balcony."
Firestone specifically took exception with Mesnick's decision to dump Rycroft on-air even though The Bachelor creator Mike Fleiss stated Mesnick was never forced to do so (Mesnick subsequently acknowledged the decision was his own during a Friday appearance on The Ellen DeGeneres Show).
"Don't drag the poor girl on national TV," he told Us. "I think the main thing, you've got to act like a gentleman."
In addition, Firestone accused Mesnick of shedding crocodile tears and portraying an "aw shucks, poor me" attitude when calling it quits with Raycroft and jumping into the arms of Malaney.
"He was faking it so much that he was crying uncontrollably and then [showed] uncontrollable elation, so he was either lying to one or the other, convincingly," Firestone told Us.
"I think it's a front -- him crying. I think it's so much more calculated. But he always tried to be the guy next door. I don't even know what his motivation was, whether it's being on TV or whatever it is."
Firestone also added he thought Mesnick's actions were "super shady."
"He keeps saying, 'Oh, nobody knows what it's like,' but... nobody would put themselves in those shoes," Firestone told Us. "Those are shoes that nobody wants to wear. He can keep saying, 'Oh, you're not in my shoes.' Well there's a reason for that, because I choose not to put those shoes on."