It would be "Calvinist."
No Calvinist teaches a believer can sin with impunity and still go to heaven, rarely or otherwise, as such would be a denial of the perseverance of the saints, which would make the person a non-Calvinist.
Banned for heresy for teaching this though? I don't know about that. Free Grace Theology teaches this, not Calvinism, and there are adherents to this theology and ideology on this site. I don't know, but I would guess it isn't an offense that would earn a ban, at least formally.