All major cryptocurrency exchanges turn into "bad guys" and only allow people to buy bitcoin and not sell it
do you think that this will have a positive impact over Bitcoin's price?
Yes, because if ever this might happen, Bitcoin will actually be considered as the victim in your scenario.
Don't you think that people will try to sell bitcoin for less and therefore impact the price?
But of course, in order for this "what if" scenario to occur and for this to happen other than the usual whale dumping or bear market scenario, there must be a radical reason why these major cryptocurrency exchanges are doing this (this is the missing link or reason that still needs to be known), of course.