The goal shouldn't be to change minds, but instead to make people see that you aren't crazy, and that you make some good points, even if they don't agree with your overall message. Make which good points and they may start to come over to your side.
The point is it's not just an unsubstantiated opinion, there is a long history of political science, involving 'critical study and evidence'. Terms like imperialist and neocolonialism aren't buzzwords like 'woke', they have distinct definitions.
As you say, such characterizations are a matter of opinion. That's quite unlike medical knowledge which is established by objective, not subjective, evidence. Generally I hear such accusations leveled at credible, mainstream sources that don't fit the narrative of those on the far left.
They aren't a matter of opinion though, there are defining characteristics accepted by a historied scholarly community that correspond with these words. There are ranges of perspectives as is common in any social science, so it is viewed as a 'softer' science compared to physics or chemistry but it is a science no less.
It may be common for criticial leftists to use these sort of terms flippantly, but that doesn't remove their meaning or usefulness in the larger discourse.
Can you explain why someone who knows what the words "neocolonialist" or "imperialist" mean wouldn't use them to describe the "global north" and "global south" disparity? I'm interested in your theory.
If anything it's the opposite. Propaganda implies your only getting one side of the issue, so the less words or concepts you know the more likely you are to have been propagandized.
You don’t understand, we need to kill unarmed people walking down a road with a drone strike in order to save the hostages. Don’t worry, we made sure we got’em all.