Different Dams could handle it different ways: it makes a difference, it just isn't "overpowered."
I'd gun for the PC to make an example on principle, not because it "breaks" the game: no min-max cheese at my table, thanks. You cheese the game, game cheeses you.
Or instead of being passive aggressive you could just, I don't know, sit down with the player and discuss the issues that you have with their build. Maybe create some house rules together to come to a compromise.
Upping the difficulty to ensure that the party is challenged? Sure. Part of being a DM. Deciding you're going to kill a character because they're named Bob and you really hate characters named Bob? Bozo No-No.
Saying "they wouldn't make it to level 10" if they did something you don't like to "prove a point" ... no. Just no.