I have no problem as I said having an alt account but when joining contests, spreading manipulated lies just because you do not like someone with an alt account is abusing the opportunity of the freedom of speech. It's personal hate and cheating.
Accordingly. Anyone can have an alt, but it shouldn't serve to defame others, especially if you don't have proof.
But unfortunately, you already know this, that when people just want to defame, they use an alt for that purpose. Unfortunately, little can be done about this.