@Riot Mastery flashing / taunting - Riot enabled griefing needs to go

At the introduction of the mastery system it was nice to see that you could earn something for playing your favourite champions but basically that's all it was. You could flash the mastery to your own team and it meant very little other than "I've played this champion a bunch, see?" but then Riot changed it. They purposely enabled it so that the other team could see your mastery spam.

I expect to receive a lot of downvotes and / or no comments on this but it really bothers me that Riot purposely enabled something that has only one purpose - to grief and taunt the other team. There is no other purpose beyond that. I have never once seen a player ask to see another's mastery symbol let alone the other team's mastery symbol(s). You can disable all chat, mute individual players and you can turn off champion voices but you cannot stop the giant visual middle finger that is mastery spam.

Riot, you have to know this. There was a reason for not enabling it at the start and then another reason for enabling it (the ability for the other team to see it) and I would love to know these reasons. I would also like to know what the purpose of flashing it has in the game beyond griefing and taunting the other team. Nobody has ever said "oh that was a nice play and clearly that person deserved it. Ah mastery spam! Well played, sir". I don't care if someone is better than me, a lot of people are, I don't care if it's used on my own team but when someone is a lot higher ranked than I could ever be dominates a game I'm in and continually spams the thing it just makes me want to turn the game off for good.