Surely, this priest has offended families who will be lost to the Church for a good long time, if they weren't lost already. However, future families will understand that they need to attend Mass for their children to receive the sacraments and that will almost certainly bring people back into the fold.
By the way, there are parishes by me that require parishioners to use their envelopes or they will be forced to pay out of parish tuition for their children at the school.
The concept of "tough love" was all the rage only 15 years ago...whereby the adult sets and ENFORCES the rules.
That concept was not wrong.
Granted that the perfection of mercy and the perfection of justice (being a unity) is difficult for humans to understand, one cannot ignore justice to be "merciful;" it's a mockery of mercy to do that.