Wait a minute, I'm confused. You seem to be on my side then. 
I don't know what your side is, but I'm against government intervention against perceived monopolies.
Maybe it's because I know that lobbies are funded by rich corporations and the like that bend the government to their will, and I am against this, whereas you think (unless I'm wrong) that the problem is that there is a government in the first place. Am I right?
I am very much opposed to lobbies bending the government. That's not democracy, it's plutocracy.
(This is a bit of an aside, but it might be fair to point out that while I'm arguing in this thread on the anarcho-capitalists' side, I am actually not an anarchist. I believe a small government is necessary and will unavoidably form in any power void. The best we can do is to make it the best possible government that represents the will of the many rather than the will of the strong.
I believe such a government is naturally libertarian with very few laws because a generally manipulative government is by definition not the will of the people. Nobody wishes to be manipulated. Also, power corrupts so size naturally begets corruption, which is undemocratic.)
It's easy to look at a market and say "you know that's wrong, I can fix that with a law." But the trap is in not asking what the costs of the intervention is. It's harder to visualise costs not yet materialised than it is to see what's immediate. Going back to the Walmart example: you want to forbid a new Walmart from opening up locally. Looks sensible, it'll "preserve competition" and jobs. But what are the costs? Decreased efficiency. People will have to pay more money for the same services and goods in your town than in other towns. Everyone only has to pay a little each, but it's death by a thousand cuts. In aggregate that's money which could have created more competition and jobs. But not just the same amount of competition and jobs: if the market got to decide where to allocate those funds it would do it in a more efficient manner leading to an overall increase in productivity and welfare.
How can any one person or group of politicians weigh these advantages and disadvantages, especially given the notoriously myopic outlook most people have on life? Then also throw in personal bias, bribes and the need for politicians to always look like they are working hard, and I don't see how there can be any doubt that every such intervention decision will actually be against the market and the will of the people as manifested through that market.
The more power government receives or takes, the greater the amount of corruption and the lesser the amount of democracy.