Don't underestimate philosophy's power to change the world. Marx's critique of capitalism had a dramatic effect, for example.
I'm not saying we sholdn't do philosophy because it can be dangerous. Philosophy can also be very good. In fact, we need the good ideas to prove the bad ideas wrong. I am a big fan of philosophy.
But not at the point of a gun (i.e., not on the taxpayer's dime). Philosophers used to be self-funded or funded by patrons. As an aside, since philosophers have become primarily funded by governments and guns, we have a 10,000 fold increase in the number of philosophers, and no increase in the quality of output.
I don't know that for certain, maybe he's just actually curious, that's why I just answered his question instead of saying this to him.
Many people think of communism when they hear the word "Marx". Few have read his arguments.
Of course, someone who quotes Objectivism in their profile is not in a strong position to talk about philosophy ;)
The open question is if government with checks and balances is stable in the long term, or if it will fall apart and have one branch take over. Time will tell.
Second, Marx made Stalin possible by setting up the necessary intellectual framework of class struggle, capitalism as oppressive, dialectical materialism (denial of reason and free will), etc.
I'm uncomfortable attributing Marx to philosophy entirely...like many historical figures it seems like he's only a partial fit. Just pointing out where your reasons leads.