How do you then explain the 'evolution' of S.P.A.M. being a forum about alternate points and mile currencies to being about free laundry detergent samples?

The TB never made that decision. It was made by moderators who decided those kinds of posts were ok to the point where postings about free samples has practically taken over the forum.

And for reasons that bewilder me to this day the current TB refused to address that issue and the alteration of that forum by the forum moderators from a forum about one thing into a forum about another thing.

The bottom line here is that unless the TB asserts its opinion the moderators by default decide what a forum is and is not.