It isn't Ford and GM fighting this, it is the dealers. I actually doubt that GM and Ford care much about protecting the dealers. My guess is, or should I say hope, that GM and Ford executives are looking at Tesla and thinking about how they might make more money with that business model in the future.
It was understood that it's not GM and Ford fighting on this issue. The point was, in reply to the OP, Tesla will be able to play the underdog card for a very very long time.
I'd say it's legitimate. If you're the youngest successful American car company and the only one from this millennium I'd say it's not wrong to do. It's similar to how Stanford is thought of as a relatively new school because it was organized in 1891, much more recently than rival schools.