It really pissed me off the other day when I had a game where I wanted to play singed top in a normal and had it banned out from under me by my ADC. He was too afraid of the "OP singed pick" apparently. It's not even THAT off-meta, it's just that the style that singed runs (especially as proxy) is so unique people think that you're trolling and attempting to throw your chance of success.
Honestly...I only get critical of champion selection when it comes to my supports when I play adc. I can deal with some of what I would consider off meta supports like malphite, galio or ashe. These champions provide a ton of utility and, while some of them may scale well with gold they don't intrinsically NEED it to provide their utility. When I see someone pick something like nidalee, leblanc or zed support I tend to immediately get suspicious. These characters need gold to get their core items to do their jobs, which means that they will usually play aggressively to get that gold because as a support they don't get a ton of farm. This is incredibly risky, in my view, and we either snowball or...basically feed. I'd just rather not take the coin toss in most cases.
Anything else goes, as far as I'm concerned. If people want to try their champion/role I take the vote of confidence that they at least know the risks and the basics of what they're supposed to do. We've all been there, where we want to try something either for giggles or genuine curiosity. It's why things like the Ultimate Bravery challenge exists.