I just had an almost really good moment with a group of students where the main guy that was arguing against me was going to have to make some pretty big admissions (he was defending trickle down economics and he was going with the old reliable"if you don't earn enough just work hard and come up with a better product so you can get rich"). However, a few people quickly started to say "well if Socialism is so good how come vuvuzuela cuba etc. etc." and this was a really tough point, because this is in Puerto Rico so one of them has been to Cuba, and he said something about how he couldn't believe the conditions they lived in. Funny enough, he just meant most people didn't own cars. But I really, really didn't want to risk saying that Cuba's conditions are actually great, or that Castro was a good leader, because that would just make me look like I'm insane to a crowd of young people who've heard nothing but "Cuba bad" their whole lives. I kind of lost control of the conversation at that point and I didn't get much progress; I'm afraid I may have even poisoned the well since I'm now kinda the Cuba Stan in a lot of their minds.
So yeah, how do you avoid this? I want to get some people to recognize that capitalism doesn't work, but it's really hard to do that when they're been brainwashed this badly. I don't want to do the "you could just be a demsoc" routine, but is that my only option? I'd prefer not to have to tell half truths about reformism being viable, but I also don't want to be the guy telling people to buy guns.
Actually is better to just come out and say it outright. It's like a seed in their mind. How silly they think your assertion is, it forces them to consider it, or to try to justify their believes with evidence, if only privately. You won't convince people overnight, but you do expand their range of thought.