There's nothing wrong with a general argument being applied correctly. Taking your lemonade example, i see nothing wrong in removing subsidies because that is removing the disease. (the disease being subsidies that skewed competition).
The reason it is wrong in the case of roaming is because you are imposing yet another regulation (not removing any). That means the actors doesn't have to shift focus towards acting in a freer market, but rather in a more restricted one.
If a ban on roaming prices was enacted worldwide do you think that would make for a more free market?
You're still focusing too much on the (rather misleading) "ban roaming charges" headline, instead of looking at what the proposed legislation will actually do ("push... roaming out of the market" by allowing people to "select... another provider for calls, texts and internet data services while travelling ... without having to change their phone number or buy a new sim card").
On the larger point, I'm fascinated by what seem to me to be the different instinctive reactions to proposals of supra-national common markets, free trade agreements, etc. by European-style 'classical-liberal' libertarians as opposed to the American brand of libertarianism.
The former generally support them, due to the benefits of having a single market - increased competition, reduced barriers to entry of other countries' markets, theories of comparative advantage, and so on. The latter, AFAICT, oppose them because they're Another Regulation which is Always Bad. Never mind that the purpose of the regulation is to remove 27 silo'd, anti-competitive, semi-protectionist national markets and replace it with a single European market.
You see the same split in discussions of anti-monopoly, anti-cartel etc. regulations - generally supported by European-style libertarians, with a view that competition is important in a free market and that may sometimes need government intervention to keep the market free, and opposed by American-style libertarians and corporatists on the grounds that government intervention should always be opposed.
The reason it is wrong in the case of roaming is because you are imposing yet another regulation (not removing any). That means the actors doesn't have to shift focus towards acting in a freer market, but rather in a more restricted one.
If a ban on roaming prices was enacted worldwide do you think that would make for a more free market?