That's the meanest and most dangerous thing to tell an incel. When you imply that no one owes them anything, by that logic, they can only conclude that they don't owe you anything either. In other words, you're giving them permission to kill people.
I think part of being an incel is that they ALREADY think they owe nothing to anybody. It's all about their entitlement, their sense of being owed; and the rage that the world disagrees.