There are a few problems I see with this response, not that I disagree with your main point.
First, I disagree that Libertarianism is an idiology. An idiology is a belief system that resists change. One prime example is Plato's Republic. In The Republic, Plato explicitly states that any deviation away from his ideal class system is a degradation away from perfection. In other words, questioning the established political order is strictly forbidden. In the case of libertarianism, I can see nothing that prevents one from questioning anything. Under a Libertarian government, one is completely free to question their beliefs, political institutions and rulers.
Second, I completely agree that it is difficult to convince enough people to join Libertarianism. But as you have already stated, this is true of all political system. No matter which system you propose or how you think Society should be organized, there will always be a challenge of winning over the hearts and minds of the people. While it can be fruitful to discuss this challenge, it does not work as a criticism against libertarianism. You can not rule out libertarianism because its hard to persuade people, let alone accuse anyone of being selfish and naive for agreeing with its values. This is because "the problem of persuasion" can be used as a criticism against ALL systems. It is thus not really a criticism at all.
The situation above is similar to the problem of explaining some regularity in nature by saying "because god did it". The biggest flaw with explanations like that is they can be used to explain absolutely everything. If your theory explains everything, then you have no reason to choose that theory over countless others. Consider explanations like "because it is destiny" or "because of yin and yang". There is no reason to choose "because god did it" over any of these two alternatives because they all explain exactly the same evidence. Evidence can not be used to eliminate your options.
The same is true with criticising libertarianism with "it's difficult to persuade". It can be used to criticise all political systems. Therefore it cannot be used to criticise anything. It eliminates absolutely every option you can think of.