Is it? I think that Netflix offers quite a lot to Comcast subscribers and far less to Comcast itself, which is the crux of the problem.
Netflix originates a lot of traffic, but it doesn't accept non-Netflix traffic for routing. That is, I can't send a request for gmail.com to my ISP, who then sends it to Netflix, who then sends it to Google. Netflix does not have a neutral network which routes traffic regardless of origin or destination - they just accept requests for Netflix and serve responses from Netflix.
No, because Comcast offers streaming video services to which Netflix is a direct competitor. Comcast would rather Netflix not exist.