Do you mean that invalidating tangle fragments increases the chance of
a coinbase tx getting confirmations? Why would that be the case?
And wouldn't that apply to any tx that someone wants to see confirmed badly?
By invalidating a fragment you earn more coins.
This argument is not convincing, since you can just replace "miner" by "attacker",
and face the same problem?!
You can't just replace miner by attacker. The payoff matrix is different for the cases of with and without coin generation, in the former case participants are not interested in approval of each other's transactions.