Reportable Offence?

I was just in a game and i pick Gangplank Support. The other people there were not happy. One person doesn't join the game because of my pick and the others were saying they were going to report me and someone was saying they knew a guy at RIOT. I am confident in saying i did nothing wrong, but i think they were pre-mades and i did feel a bit threatened. So what i'm asking is this; Is picking Gangplank as Support (which is totally doable) a reportable offence?
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