The point on my argument is that solipsism is not a position that can be hold rationally and consistently, because holding it implies not being alive, so no one can ever claim to hold that position in a rational and consisten way.

And also, it is not that it has no usefulness, it is that is impossible to hold. It is a fun mind experiment, but not a position that is rational in any way.

Besides being a suicidal position, it is also a position that implies that no discussion makes sense, because if you could believe in solipsism, there is no way that you can discuss anything with anyone else, because you don't believe that there is anyone else.

So, again, fun mind experiment, but if you hold that position, you are being inconsistent and irrational (not saying that you hold it).

I would argue that solipsism or any philosophy that states that reality is not real can not be hold by living beings while being consistent and rational about it, because this kind of thinking would define air as not existent really, making it absurd to continue breathing, and then dying.

You can repeat that with food or any other requirement for survival.

While this things can be interesting in some context, any discussion that don't accept the pre-conception of an objective reality outside our mind is not sustainable. Of course, this aren't the only ideas that can't be hold with consistency and rationality.

What definition of vaccine do you have that the antivax take is not bs?

If you take any scientific vaccine, this is the answer to the antivax take. It is reasonable to be antivax for example, when the vaccine proposed is the piss vaccine used by crazy cults, but the scientific ones don't have the flaws attacked by the antivax crazies.

This doesn't mean that our scientific methods, or that the process that we used to develop vaccines, or that there isn't corruption in our institutions that we need to fix, but the problems aren't related to what the antivax cults cry.

No, but anti-vax and climate denial don't have any real foundation in reality, and work with conspiracy theories and religious zealotry and not with evidence and logic on their side.

So, we have an ethical responsibility to evaluate things.

If we go to real scientific theories, we must demand good evidence, definition and consistency in them, and depending on the topic, this is normally provided. The main scientific theories that the scientific community tends to hold, already hold enough evidence and information to be accepted, but the important point there is to also accept that if we found more information and those things need to be discarded, we need to accept that.

Let's take the example of climate change.

One of the lasts reports on climate change explained that we can't stop climate change while still using our capitalist approach, that revenue needs to drop and change our paradigm completely.

This is a realistic approach, one that reviews the data and explains what needs to be done in order to fix things. But, the persons that needs to do something are the ones taking advantage of the current system, and sell the optimistic position that we can fix things while keeping the same system, again, something that was proven completely incompatible.

So, the two realistic positions are:

a) people in power will not change in time, and humanity as we know is doomed.

b) we need to make radical changes and quick, making a lot of sacrifices in the process, in order to have a possibility of surviving.

None of this positions are optimistic, and both can be defined as pessimistic in different ways. Optimism never helped to change things, it only helps to keep the status quo, if the status quo is good, great, that is a good thing, but most of the times is not, so optimism in general is negative.

Of course, going to the extreme in pessimism is also not good, because extremes are bad, but the spectrum of options in pessimism are much more positive than the ones in optimism.