Why do people on my own team ban my champion?

Its actually been happening so often now. I cannot believe it. I prepick my champion and it gets banned my own team mates. I picked Brand support and its banned - team mate says - Brand isn't a support?? Ok I guess he isn't the most ideal support but he is very effective in low elo if you cannot rely on the ADC to carry. Another lobby today, a player decided to troll because someone else banned his champion.... he took smite ignite and went bot lane but I dodged this lobby too. I am incredibly sick of this, why are there no punishments or a system in place for this?? %%%%ing riot.
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