Thanks for posting this. However I think this is an area where our opinions differ. I don't see an ethical problem here. Essentially the professional guide friend is asking Rick to help enforce what he believes to be the rules even though the local authorities aren't enforcing them! It seems to me that the guide should be making his case about legality somewhere else, not to Rick. Or perhaps as a guide wrote on Ricks blog it isn't actually illegal after all...
There are some legitimate points raised -- how good are the tours? But just as Rick isn't obligated to mention every B&B offering rooms but only those he approves of, same thing applies to tours. If Rick or his researchers have taken the tour and found the presentation acceptable, then by all means recommend it. Sure I'd like guides to have full-time jobs and a good living. But they aren't entitled to it any more than buggy whip manufacturers or anyone else who's job prospects have been reduced or eliminated by changing mores or practices. Maybe the "free" tours have just come up with a better business model that satisfies what tourists want. IMHO the real question isn't whether RS should censor his book and not mention them, but whether tourists want the world that results if they use them. Just as you may buy from Amazon instead of your local bookstore, you may decide to take the "free" tour. This changes the local economy just as Amazon does for booksellers. If people value what the local bookseller or full-time tour guide provides over the alternative, they will survive.
As for "free" being misleading, I think Rick answered this himself. He gives "free" talks in hopes of attracting business, hosts a "free" PBS show that is wonderful advertising for his company, and so on. I don't think anyone is so gullible to think they won't be asked for a tip, any more than I expect to see the "free" Shakespeare in the Park plays and not expect them to ask for donations at the end.