through treachery and deceit,

Oh and you think the oppressive Starks haven't used treachery and deceit in the past to control and seize? Their whole reign was nothing but slaughter and murder! It's all a matter of who the winner is and how it is defined by the history books. Good Lord Ramsay has 20 Good Men re-writing history to omit the Stark name from everything.

he has no claim to it

Possession is 9/10's of the law.

Lannisters THE King legitimized him as a true blood heir through official proclamation for all to come and see

FTFY

all the blood claims the Starks

After Ramsay's impending glorious victory at the Battle of Winterfell nearly the complete Stark bloodline will be dead. So HA! There will be no Starks left to make any claims!

What can a house from the Westerlands know about the North?

Like Jon Snow they know nothing! But that matters not as Lord Ramsay has taken the initiative and become an independent separatists! Something the former lord of Winterfell didn't have the balls to do. Now the people of the North are more independent as they have no fealty to the crown, just to Lord Ramsay! Our good Lord Ramsay has benefited the commonfolk in many ways - apparently simple minds like yours fail to comprehend that!

The only Lord of Winterfell are Starks! is Lord Ramsay Bolton

You seem to not know facts. Our Lord Ramsay is going to send out 20 Good Men out in all directions to hunt down anyone who mutters those words again, and banish the name Stark from the Northern vocabulary. So far the list of words that have been banish from the Lord's official language use list are: bastard, Stark, Snow, traitor Theon, Hornwood .