Au contraire. Net neutrality supports market efficiency, the same way that building a national highway system did. Incumbents want to raise their margins by decommodifying their services to confuse the market.
Now, creating regulations itself is inherently anti free market (just as collecting taxes to build highways was). Perhaps in the future we'll have ISP startups competitively bonded with prospective subscribers, and private covenants assuring what types of traffic will pass (although why would subscribers choose anything other than "all", given the majority expense of a last-mile ISP is the fanout). But until that prospect is even on the horizon, it's a moot point. Any proponent of free markets, even a dedicated ancap, should support the approach that results in markets actually functioning freer.