Whether or not you agree with what he said, HOW he said it was incredibly rude, unprofessional, and insulting to adult fans, whether they've voiced anything for/against the show or not, and I do believe he should be censured by Saban and Nickelodeon for this outburst.
Regardless of the "no one under age of 13" rules on Facebook, everyone is fully aware that there are children on the site, either with their own accounts, or using their parents/siblings' accounts to access their "heroes'" pages. Additionally, these children may be young enough that the lines between fiction and reality are blurred, and while, inside, they know that these actors cannot actually turn into Power Rangers, and may or may not realize that they're doing choreographed fights and possibly don't actually know how to fight, they will still equate "what actor says/does" with "what character says/does."
Again, it doesn't matter what or why he said it, it's the HOW he said it. He was rude, unprofessional, and insulting. He used profanity, both explicit and implied, on his official page, where, I'm assuming, he presents himself as a member of the cast, and, therefore, an outlet of the show and production. Whether or not he is an official/authorized outlet or not, in the eyes of the general public (both adult and children), he is representing the show. And, especially with the allegedly offending posts removed, so there's no context for his comments, his vitriolic words reflect poorly on the show and the standards held by the company. Therefore, as I said before, he should be censured.