Complete Bollocks..
Only time Rossi ever did anything out of the ordinary was stopping the little .... after he nearly wiped him out with a swipe across the bows.
It resulted in Rossi losing his 10th championship (in my eye)..
Really... lol
Here is a little exercise you can do for yourself and it will disprove your theory (I've actually done this and it all checks out).
Go to the MotoGP website, download the 'analysis by lap' race data .pdf for the 2015 Valencia race.
Lorenzo, Marquez and Pedrosa ALL lapped faster than Rossi did on every single lap of the Valencia GP.
Rossi, all credit to him did an admirable job from going from the back fo the field to 4th (whether Petrucci or others let went easy on him and let him through without too much of a fight or not), seriously. Made the hairs on my back stand up, was proper awesome and riding to save his life. Kudos.
But the actual laptime data shows that even if he had started in 4th position.... He still would have finished in 4th based on the laptimes... the only difference would have been how far he finished behind the front 3 leaders.
The only argument is 'did Marc go easy' on Lorenzo to allow him to win??? Its not something you can prove or disprove, nor against the rules. Regardless.... if the rider truly deserves to win the championship its because he is the best and strongest rider and will beat anyone who stands in his way to oppose him.
If Rossi was the fastest and best rider who deserved to win, then he would have been lapping faster than the 3 who finished before him that day. IF that was the case (it wasn't) then you could argue the start at the rear of the pack at Valencia cost him the win but clearly not the case based on laptimes that day.
Now if Marc went easy or not on Lorenzo... well thats just to bad. The strongest rider should decide the championship by winning and being the strongest.
Rossi going all area 51 (playing mind games) and putting Marc on the spot like he did in the PI press conference (and comments he made in the Italian media about Marc lying about putting Rossi posters on his wall as a child...lol) backfired.
When you are the strongest rider... then you make the calls. Either Marc or Lorenzo was stronger that day, either way you look at it Rossi wasn't the strongest and because of that he couldn't claim the title. If he was the strongest he would have wiped the floor with Lorenzo and Marc at PI, Sepang and Valencia...
You cant blame other riders for the fact you cannot beat them.