In all honesty, I doubt this meme makes people think twice about themselves.
To the people being called npcs, it's just another right-wing buzzword that will be ignored. As for the people saying the meme, they also won't reflect on their own views. If you view your opponents as mindless cattle, you're not going to take their views seriously and challenge your own views.
You could say that the people being called npcs maybe should reflect on their views, but the people calling them npcs aren't saying it because they want to change their mind. They say it because they aren't worth talking to in the first place, which is why they're called npcs. It's used as a politcal insult, and people will take it as a political insult instead of criticism.
Ultimately I don't think the term really does any harm. It's just a reflection of the current political climate. Nothing new or insightful is being said. It's just a more effective way to say the same thing.