Leave campaigners are perfectly entitled to disagree with remainers. But to say that anyone in support of Remain should keep quiet is a bit much. It's everyone's responsibility to argue for their case, especially over such a massive decision.
If Major had been gunning for the LEAVE campaign, we wouldn't be hearing all this aprobrium. As a great many of our resident right-wingers probably voted for him in 1992 and 1997, its a bit rich to start bad-mouthing him now !