Like shopping on Amazon, or buying from China, I'm going to do what's best for me as an individual. It's government's job to step in and tweak the playing field to keep it competitive, and I'll happily vote to regulate the very things that serve me today, whether that's breaking businesses up, preventing mergers in the first place, having businesses pay for their externalities, etc.
An example to which I could relate in terms of this line of thinking is plane vs. train travel. Were subsidies to flow towards the train rather than the plane, it would make it more affordable for me to the environmentally better thing. However, as things stand, I frequently find it hard individually to justify the often much higher cost AND longer duration of the train over the plane.
All sorts of ramifications of the current system are awful for me as an individual. I don't want pollution, slavery, and all sorts of other problems, some of which directly affect me. But within the existing system, it might be my best individual choice to still buy a product that has those problems in its production because the alternatives available give me a worse experience.
The whole point of government intervention is to change the situation so that we don't have this dilemma.
I don't want the externalized costs of certain cheap conveniences! But if everyone else keeps doing that and I refuse to go that way individually, I still get the externalized costs anyway! I don't HAVE an individual choice that will eliminate those costs. If I did, I actually WOULD choose that over the cheap conveniences.
Liberal ideology requires a god-blessed sovereign that lives outside of the system and has no motivation other than the common good for his subjects - whether that's a king, a magical computer that makes provably optimal inhuman (i.e. objective) decisions, or an army of biracial, bisexual, ungendered university professors who were in the top 2% of their class in elite colleges. There is no government, and no means of governance, that lives outside of the human struggle for power. Governance is the wielding of power.
You can't just wait for power to be placed in the hands of the just. The just are the ones who are willing to forgo power for the sake of the good. There will never be a magic button that you can push to make everybody stop benefiting from the bad thing at the same time. The kind of government intervention you're asking for is divine.
You have to take a risk, to be weak on purpose. Hobbes said it best in Leviathan: you have to make a "covenant" with the world, a contract that you will follow for the sake of others whether or not others follow it. An oath that obligates you and no one else, with the hope that others will be inspired by your vision for the world and live the oath themselves. The combination of you and those others creates power.
[$] Everybody is willing to be inconvenienced in some way for some value, everyone has some value that when violated will effect their personal comfort more negatively than some marginal degree of convenience will improve it.
Regardless of all these other things, there are also situations in which the collective-action any individual might choose (even for selfish reasons!!) if they had the magic button is not the action they would choose as an individual without the coordination of others.
So, however it is accomplished, in whatever political system, there are cases where merely enabling a group of people to act in coordination allows them all to pursue their individual interests more effectively.
The core point being: you cannot merely judge that people who refuse to unilaterally follow a contract that others reject means that those people do not support the contract.
Put another way: Kant's categorical imperative is a nice concept, but it's delusional to actually think it represents reality rather than just a mental model.
If I self-sacrifice without collective action, I might very well reduce my own capacity for other positive actions and convince others by my example that self-sacrifice is counterproductive.
You might think you'll be better off of the tax rate went up by 5% (say) but you'd certainly be worse off of you alone started paying 5% more.
I can't speak for that commentor but from what I've seen most people who say things like that just dont want to take any responsibility. The attitude is: I do what I want today based on my immediate wants. Its maximum freedom! But I want the government to protect me from others bad behavior. And if they do try to regulate or break up a company that's giving me what I want, imma complain about it because it may interfere with my choice.
It's a combination of narcissism and lack of personal responsibility.
Edit: and that last part sounded really shitty. Maybe I need to change who I hang around so I see less of that.