That is different. The OP wants to take a 14 year old kid who can't go on the rides on a tour that he is probably less than 2 years shy of being able to go on so that his vacation is not ruined; that is not going to be the gateway of lies and sneaking into bars underage. That's just silly. Obviously, a 14 year old is going to know right from wrong and know that going on a 16 and over tour at Disney World isn't going to have consequences as would sneaking into a bar underage or lying to their parents would.
My mother used to help me sneak into places; when I was 14, she helped me get dressed up like I was 16 so I could get into a taping of a show where my favorite band was performing. I turned out just fine. And to think, I could have taken from that experience that it is ok to lie and sneak into bars underage. Darn, I missed out.
Honestly, I think you're making a big deal over nothing.

The 16 and over rule is, like other posters have said, there so that small children cannot get in, probably because it will ruin the magic, perhaps, and also because it's a long tour and small children are probably an interference at points.