Verizon could have legitimately argued artificially throttling at the Level 3 connection is necessary to protect their network. But they didn't say that at all. They basically bragged that their own network is running well under capacity. The insinuation is that Verizon is ready to handle all the bandwidth that anybody can send, but that Level 3 was over capacity.

But, assuming they really did need to throttle traffic in order to protect their own network. For one it wouldn't make sense to control your throttling by running your routers at 100% capacity. But also any throttling should be equal among all of their peers and not selectively chosen based on Verizon's business interests.