Definitely not a socialist but big companies hurt consumers as individuals and other businesses and society as a whole. Not by default, eg MS of today but due to their tendencies.
Monopolies aren't inherently bad, they're regulated because they incentivize anticompetitive behavior that hurts consumers and the economy in the long run (you have to assume companies will act against their best interests for them to not cause problems). Megacorps aren't inherently bad, but we may want to regulate them because they may incentivize anticompetitive behavior that hurts consumers and the economy in the long run.