It's not really double dipping. Again:
Imagine if two companies wanted to exchange physical packages. And assume that each package exchanged equally benefited both companies, say each company made $10 for each package exchanged. Should each company bear their own costs in exchanging the packages?
Well, if the costs were roughly equal, sure. But what if they were wildly unequal? Say one company had to carry them across an ocean and the other only had to carry them across town. And yet each package carried benefited both companies equally. Then wouldn't it make sense for the company that has to carry the packages across an ocean to also get some money from the company who only has to carry them across town? (Roughly half of the difference in their costs to carry the packages.)
The company that only has to carry the packages across town could say, "The other company already makes $10 for every package exchanged, paying us would be double dipping". But that's clearly nonsense.
Content providers like YouTube and Netflix can locate their servers in datacenters where bandwidth is absurdly cheap. They're like the company that only carries the packages across town.
ISPs like AT&T and Comcast can't ask their customers to move into datacenters. They have to build massive networks that cover cities. They're like the company that has to carry the packages across the ocean.
And it's reasonable to assume that data exchanged between a Netflix server and a Comcast customer benefits both companies equally.
This is the rationale for settlement based peering. And this is the arrangement the free market has worked out over decades. It's been reliable and stable and has fostered the growth of the Internet with relative freedom from regulation, fairly splitting costs between content providers and access providers. Now, one side wants the government to strong arm the other side into getting them a better deal than the fair deal the free market got them.