I think there are some assumptions being made here that if they are not true, I certainly would call slander, and I think they would interfere with him and his boss earning a livelihood.

I haven't heard it said that he was illegally operating as a plumber without a license. If that is so, he should be shut down until he can get a license. If he is defrauding people by stating he has a license, he should be prosecuted. If it is just that it is generally better to have a license, that people are well-advised to preferentially hire people with licenses, no argument here. It is better. There are other circumstances...many financial...many educational...I don't know why he doesn't have a license. It sounds like he was at least operating under the assumption, for many years (years when it seems the boss would have been shut down at some point) that he was legal at least in parts of the township or whatever they have. I don't know. If he is doing something crooked, throw the book at him. If he is an honest working man, who might have skills that most of us could never acquire (I don't know..maybe he just unclogs toilets day and night)..he should be encouraged to get his license etc. etc. I personally think twice before doing or stating anything in a very public forum that comes between a man/woman and a job.   mg