The Conservative leadership during that period is still one of the biggest stains the right has. The politicised aspect of the show (i.e. JTBC being right leaning, the elections in a few months etc) could and I think (hoping anyhow) is just a coincidence. But if your the right-wing in this situation, anything that legitimises some of the actions undertaken in that period is a small step.
By showing there were North Korean spies posing as students is one thing that provides credence to the arguments used by the ruling party to search, detain and oppress students. Whether the ML has taken part in the protests or not isn't relevant (and we currently haven't see him do that), he's still there with the pretense of writing a thesis. Scheming happens on both sides.
You'd want to influence younger minds as they are the future voting population and are also easier to influence in general, especially through a huge kdrama. I don't think you can swing either way on whether this is being pushed as propaganda or not yet. If the things about the writer and her husband are true (and she sort of has history with Bridal Mask), it would add more credence to the argument it is though.
In the most recent posts I was reading on the qoo, there were a couple of them about BP and koreans were legit calling them "Ilbe group" which were pretty shocking insults. Seems like Ilbe and right wingers are going all out on promoting this drama apparently which is another part this scandal is so huge.