Relativism is the belief that everything is a matter of opinion. It underlies post-modernism, which is the fashion in academia today trying to replace Marxism as a systematic type of thought. People who oppose science are superstitious or mystical. We Marxists may say they are pre-capitalist in having reactionary ideas dominant prior to those of the Enlightenment. The ultimate mystical ideas are religion, which cannot be falsified.
Science is partly production of falsifiable theses .
It means that there is evidence conceivable that could disprove the thesis. The belief in God as practiced by Christians, Muslims etc. is not falsifiable. It is simply a belief in authority. If in the year 2100 it turns out the bourgeoisie was the class that worked hard to bring about communism, we Marxists would have to concede that one of our theses was proved wrong and look for a replacement thesis. Such an attitude would be unscientific dogmatism.