This sounds like a canard. If by "regulate more" you mean the available profit margins are smaller, then yes. However, if profit margins are very high, you can place quite a lot of expensive regulation (not all regulations are expensive, some of them tell you not to do injurious things) and people will still invest.
By its nature, content will drive a huge amount investment. Funneling bits at high speed is an interesting business, but the recombination of those bits has a universe of more possibility in it. I'd be surprised if (after the ecosystem reaches critical mass) content investment always dominates infrastructure investment.
In any case, the case for neutrality is stronger than an abstract argument against an arbitrary regulation. The promise of the internet is that of decentralized many-to-many content generation, i.e. the strong airing of many different opinions by large and small operations. When the people that own the pipes can pick favorites, the strong voices will over time winnow to the favored ones.
This is a pattern that happens over and over again in US media where large corporations are able to pick ideological favorites and narrow the spectrum of discourse to suit themselves. Network neutrality being knocked down is a strategy of corporate dominance over public discourse. Note that very few, very rich, cable companies provide most of the telecommunications for the entire population. Granting them this power allows small groups of individuals with many common interests to pick favorites to a startling degree.