how do you know that all exchanges are scam or maybe you have been hit by a scam coin project so that this is not a good issue you better learn a lot and be careful in buying and selling on the exchange before buying you must know the risks you will get.
Or maybe he lost a lot of trading that's why his very angry in every exchange. Exchange are building their reputation by thier own even how small or big it is you should always know a trusted exchange to use which is the exchange with a lot of users so that way you will not can't be a vicitim of scam exchange like what OP saying.
And if you lost in trading its normal and its part of the game.