It normalizes the methods they use to transmit their ideas, and the ideas themselves. You are not immune to propaganda. You cannot entirely control the systems you use to process information. The more you use and reference an idea, the more makes its way through it. The more familiar something feels, the less you are able to question it.
It doesn't matter if you are joking. It doesn't matter if you are being "ironic". It doesn't matter if you are "on our side". Your actions have consequences. Spreading fascism is spreading fascism.
If you do this, there will come a time where you realize the people around you aren't actually joking anymore. By then it will be too late.
This impacts you even if you aren't the one saying it as well. Consuming propaganda leads to the spread of propaganda. As you use systems to process information, others must reference those systems to understand the output. Every time someone says "too many people exist" overpopulation pops up in your head. Doesn't matter if you agree with it, it's there.
This can be helped by engaging it critically every time it happens, by breaking the flow of normal conversation and interaction when it comes up. This will not fix the issue, so don't over rely on it.
Many platforms allow you to tag specific words to either remove the message or warn it. That is one way to break that flow, so it doesn't skate in under the normalcy of the regular consumption of media.
Add fascist shit like "IQ" there.
Add fascist conspiracy theories like "overpopulation" there
Add "sanity", and all that references it there. All that references is whether you believe in hierarchies after all.
Add ableist language like "dumb" or "stupid" there.
Break up what you consume. Give yourself the ability to stop and think about it. This has really changed how I approach media and interaction.