Boy, if THAT statement doesn't open you up to a libel lawsuit, nothing does.
I find that funny coming from Pete who for years ran a business that did nothing but serve underage kids.
First, Mitchell would have to locate "the Mechanic" to file the lawsuit.
Upon filing the lawsuit, the burden would be on Mitchell to prove the statement was false.
In addition, arguably, Mitchell has made himself a public figure by becoming a published author of a weekly column. That would make any libel suit even more difficult than for a private citizen because, not only would he need to prove it was false, he would need to prove it was made with "actual malice," and/or a "reckless disregard for the facts."
In addition, by filing the lawsuit, Mitchell would most likely be opening up his business operations to pretrial disclosure, including whether or not he (or any employees) had ever served an underaged person, what training the staff got in Dram shop, etc., any investigations or fines from the NYS Liquor Authority, etc.
Does all that really seem worth it to address an anonymous statement on a message board?