They seem to want to be obstinate, so while I don't agree, I'll take a stab at answering the question:

The link they posted has this bit right at the top:

You may have paid money to get copies of a free program, or you may have obtained copies at no charge. But regardless of how you got your copies, you always have the freedom to copy and change the software, even to sell copies.

The fundamental belief seems to be that however you obtained the software, paid or not, you should be free to do literally whatever you want with it.

Where I really disagree is that proprietary software (like half of the answers in this fucking thread lol) are fundamentally not scams. A "scam" implies something that one party, the patsy, is not aware of.