I happen to be one of those people with an absurdly high mastery (1.5 million on Diana) and I do not like having this displayed. I feel like it has only created a worse environment for me as a result of enemy players seeing this as well as my team mates. My team mates often flame me or say passive aggressive things in the beginning of a match. One I that I still vividly remember, "I know who to blame if we lose". Spoiler alert we did lose and it was because that person fed. I feel like this also leads to me being targeted by the other team. I have played so many games this past week where I've been ganked very early by jungle and top lane, or jungle and bot, or all three, upwards of 5+ times during laning. Not saying some of these ganks weren't sniffed out but it definitely seems like the enemy teams have been bloodlusted for me this season.
I do think whether or not it should be able to be disabled for enemies is a bit of a gray area and worth having some debate about. I don't think disabling it for team mates is as big as a gray area though as it has done nothing but tilt team mates before games even start.