Ente's accusations against Proton, is it their new marketing?

Not if it’s handled properly. Removing the original post would prevent false information from continuing to spread, while leaving the apology to Proton visible. There’s no need to link to or quote Ente’s original incorrect claim in apology tweet. The problem is that the original tweet is still receiving much more attention than the apology, so many people end up seeing only the false accusation and not the correction.