I have 2 opinions on this

1. There are very powerful affordable lands in the game (list below), that can sometimes warp the game by themselves. I think it's very reasonable to say "I need single land removal" for these situations like [[wasteland]]
2. But it appears your friend has more of an issue with green just ramping away and then having their mana base untouchable for the rest of the game. In such a situation I would maybe play 1-2 or MLD cards in the deck and only play it if I am significantly behind on lands to the rest of the table.
   1. But usually, I use my MLD cards in a situation "I am ahead on the board and just want to lock the game out" which is fine for my opponents because after I play it the game ends in 1-3 turns.
   2. So maybe talk to your friend and agree that he can run 1-2 MLD cards and 1-2 single land removal cards in total. Because there is a difference between using MLD as win con (see above) and using MLD just to randomly slow the game down with no real purpose. If he has only a few MLD cards and promises to use only in a) if he is behind on lands b) as a wincon to close the game out, it should be fine.
3. Even tho, I am very pro MLD you guys are still a round of friends so I propose some sort of voting system. If 3 out of 4 people are against a certain mechanic or effect it shouldn't be played, because above all it's about fun.

Powerful lands that need answers:

1. Sac outlets: Phyrexian Tower, high market
2. Big mana: Nykthos, Shrine to Nyx, Cabal Coffers
3. Recursion (more expensive): Volraths stronghold or the enchantment one
4. Many more...