Most people complaining about Riot's stance on meta breaking dont know what the 'meta' is.

Meta is often a word just casually throw around but it can mean two different things in the context of LoL. There is the champion meta, the champions that are currently deemed the strongest or overpowered, most over influenced by competitive play. There is also the meta from a strategic point of view, or how the game is played, ie lane assignments, 1 top 1 mid 1 jungle 2 bot.

Picking any of the champions in the game for a specific lane assignment is not considered bannable by Riot and is not breaking the meta as long as you are trying to win. You DO NOT have to pick your champion according the champion meta, you're absolutely free to pick the champion you like the most or feel is the best.

Nunu smite 'support' is breaking the strategic meta because hes not really a support at all. He isnt 'just roaming', hes leaving his adc to 2v1 bot the entire game, resulting in that player having a miserable experience. Hes also very likely ruining the experience of the jungler on his team by stealing camps ect. The problem with this is that the other 4 people on his team queued up expecting to play a certain way, a way conforming to the strategic meta. Nunu smite support is breaking that meta and FORCING 4 other people to adapt to his specific playstyle with no communication or consent from the other 4 players. This is not only extremely selfish but can ruin the experience for the 4 other people on your team.