Should you be allowed to play less seriously in normals over ranked? Obviously.
Hell, I would say that I'd be down with someone playing Yi support in normals.
I just ask you don't troll others because you don't feel its as necessary not to, don't ban champ picks, don't blast cone me into Dragon Pit while they're doing it. Keep your idgaf sphere of influence to yourself, once you start griefing, the game type no longer excuses you.