If there is any ill-intent present, then there is no point asking them to disable RBF because they would have gone a little further to try to get their transaction to get double spent.
That's true, just wait for a couple confirmations and you're fine. RBF or not.
There's this misconception that disabling RBF prevents any easy double spending but that is false; the primary purpose of RBF is to allow users to replace their transaction with another that spends a higher fee and disabling defeats that purposes especially in instances where fees spike were to occur.
Yes, but it also makes it difficult to reverse or replace the transaction. If I was a merchant I'd rather accepting a low-fee unconfirmed non-RBF transaction than a high-fee with RBF enabled, because the latter makes double-spend easygoing.