Science never says to choose communism or Marxism over total free market anarchy (capitalism) nor the reverse.
Science never says you should take vaccines nor not take vaccines. Science never says you should not feed your dog or cat a vegetarian diet nor that you should. Science never says you should choose your cat or dog over chickens, pigs, turkeys in factory farms, nor vice versa.
Science never says you should or should not test/experiment on animals. Or on prisoners. Or on politicians.
Science never says you should nor should not fight for your country.
Science says ONLY that IF you do this thing, then (within some range of probabilities) this OTHER thing will happen.
If you continue to burn X amount of fossil fuels, then earth's temperature will rise this much.
If you feed your cat or dog this cat food or dog food, then this cow or chicken is forced to breed & produce this other cow or chicken in this factory farm, and this amount of suffering takes place.
If you don't fight this potential threat in this other country, then that threat will grow with some probability, P, and make that other country unlive-able for people who prefer democratic elections, but to fight it, this number of other people will die.
Science is about making assertions of X->Y, "X causes Y", as quantifiable & falsifiable as possible. By contrast, words like "nationalism" or "capitalism" or "socialism" or "communism" are generally unfalsifiable.
Actually, nationalism IS a slightly more falsifiable, testable word: saying I'm "fighting for my country" implies you have to benefit THIS PARTICULAR set of persons or individuals that make up your country.
And, while you can certainly sacrifice a lot for a cause, and that cause can do a lot of good, for some group of individuals (nonhuman animals included), often who exist in some OTHER country, that doesn't mean it benefits YOUR country. it doesn't benefit the animals or the prisoners or the poor in YOUR country.
Again, science never said that EVERYthing you do NEEDS to benefit EVERYONE in the world or your country all the time. Making your sacrifices for others can still do more good than not making those sacrifices.
Therefore, it is ILLOGICAL & STUPID to say any particular political cause - communism, socialism, capitalism, anarchy, fetus rights, gun rights, anti-gun, healthcare for all, healthcare for nobody, antinatalism, animal rights - is "anti-scientific".
But, if your cause is promoting a provably false scientifically false belief like "flat earth" or "AGW isn't real" or "evolution isn't real" or "9/11 was caused by thermite explosions", again - science doesn't say not to promote falsehoods, nor to not promote them. Science simply asserts that the belief is false.
Logical consequence of this: Science says NOTHING about what one's political (= ethical) position is on ANYTHING. Whether good or bad.
Therefore, it is IMPOSSIBLE/ILLOGICAL to say anyone's particular political opinion - about what should be legal or illegal - who should or should not go to prison - is "mental illness" or "mentally ill". These phrases strongly imply / suggest some sort of BULLSHIT imaginary "objective scientific" position.
I only call others mentally sick/ill for THEIR political opinions when THEY start attacking MY position with their insults and name-calling of "mental sickness/illness" because it's just more practical than going into all these subtleties that they are too stupid to understand anyway.