Taypayers aren't paying for those children. The children are the ones paying for the bad situation into which they were born. When they grow up in a small, suffocating, welfare world, where getting out can be impossible; and daring to dream isn't what anyone else around them does; they continue to pay when they approach life as if that's the only way of life there is.
What taxpayers are paying for is sometimes the failure of some parents to be able (either through no fault of their own, or as a result of their own failings) to raise children who see possibilities in their future, beyond confirming their own grown-up-ness by having babies. Taxpayers are also paying for the kids that get forgotten in public schools. They're paying for a system that does little to support (I don't mean financially) families and independence. They're also paying for courts that screw up in one way or another, and they're paying for every welfare program that doesn't even recognize the concept of "the capable individual" and, instead, believes every person who has a money problem MUST need someone else to become their permanent "parent".
The taxpayers also pay for their own failure to make a few efforts to understand exactly why things in The System are so wrong, and they pay for voting in people who can't/won't identify problems and fix them - rather than throwing money at the same old problems that have been around "forever".
In answer to the question, nobody has the right to "permit" anyone else (or not) to have children. In fact, sometimes those children are the only bright spots some of those parents have ever seen in their lives, or ever will.