I do not see it as an anchor baby but as a gift to the baby. If they stay in Canada and apply for citizenship eventually, the baby will also be included on their application and will have dual, US and Canadian or even triple if it also gets citizenship from their home country.
They would have to sponsor it but it's not a big deal because the baby is a US citizen and visa exempt to Canada. All they would have to do is bring it across the border and then file to sponsor. It's not like being stuck in a non-visa exempt country with a baby born there and not being able to go to Canada without trying for a TRV-TRP or leave wife and baby behind while the father goes alone to Canada to sponsor.
I don't really have a problem with baby tourism as long as they pay their hospitals bills and don't leave them to the tax payers to take care of. If the US didn't want babies born there to have citizenship, they'd change the law. So could Canada.