It's not all that different from a player who stales out and wrecks his nation's expansion, or worse, a player who abandons his position and throws all his gems and lands to a neighbor to "make friends".
Hopefully the other nations in the game will take notice of who gains an instant power increase by eating him, and rebalance the game by attacking the "lucky" beneficiary of the abandoned/underperforming nation.
I mean, the cause of the problem is different, but the response can be the same.
It's hopefully a learning experience for the underperforming player, and hopefully he will ask for some advice on how to expand and/or protect himself better. I would never kick someone from a game just for being inexperienced and/or unskilled.
Edit: There's also nothing stopping you from giving advice in-game before it's too late. I've urged newer players to buy at least 1 PD, when my scouts have seen their lands undefended (if it's not possible for me to launch my own scout attack
).