That a Republican Senator says that health care is a privilege, not a right, won't be all that much of a surprise to anyone. That this then enrages some on the left is equally unsurprising. The thing is though Ron Johnson is actually correct here.
Someone has to pay for it
A standard distinction in philosophy is between negative rights and positive rights. The importance of the distinction is that no one has to pay for negative rights, they just have to stop doing something.
So, the right of free speech just means that no one should or can stop us from speaking our minds. Positive rights are fundamentally different, someone will have to provide us with that thing which is the right. If food is a right then someone has to grow and provide that food to us. It actually costs someone else to provide our food.
Health care is a positive right
health care clearly costs something to provide. Thus it is, by this classification, a positive right. Or, as the same philosophic distinction makes clear, it's not, in fact, a right at all, it's a privilege. For once we decide something is a right then other people are duty bound to provide it.
Free speech as a right means no one should stop us. But as Ron Johnson goes on to point out, quoted in Salon: "...the minute you consider health care a right, well, who's going to satisfy that right, and what does that make them if they are forced to provide you with that rightful product or service?" Can you, should you be able to, simply turn up to a doctor and demand that she treat you at no cost? For that is what the insistence on health care being a right is actually saying. And the answer is no, we cannot nor should not be able to do that. Just as we cannot demand free food from a farmer or the supermarket nor shelter by taking someone's house.
Health care is a desirable privilege but it is still a privilege
The insistence that we get this correct over rights and privileges does not mean that there should be no public supply of health care. Not at all - for the same reasons that it's entirely correct that we have a welfare system which provides those other privileges, such as shelter, food and basic living expenses. We do indeed want people to have these things. There will be some people who cannot afford them from their own resources, therefore, society aids them in gaining access to them. This is all entirely fine and acceptable, moral even. But it is still true that these are not rights for someone, somewhere, must pay for them, someone has to have their resources taken from them so that the privileges can be offered to others.
We should, and most places do, have a public system of providing health care to those who otherwise could not gain access to it. But this is still a privilege, not a right, as quite obviously the public must be taxed to provide that health care. Senator Ron Johnson is correct here - however much it irritates some people.