Trying to share our understanding with the uninformed, misinformed or the contrarians, can be challenging and frustrating. However, I can tell you with absolute certainty that no one is going to be listening, once you've insulted them, or their opinion.
The people you are talking with will have expectations that you are going to say just about anything to advance your cause and given what I've read from some of the anti-captivity proponents, they have good reason to expect so.
Educate, don't berate.
My advice to you is this: Be a model of intelligent, fact based, rational behavior.
Rather than shaking your fist in the air with righteous indignation and a, "You don't know what the hell you're talking about, you f***Ing idiot!" instead, be reasonable, rational and factual.
By communicating in an intelligent and respectful manner, it demonstrates that you are thoughtful, carefully consider what you say and therefore, more likely to be seen as credible and believable.
It's wise to remember that there may be someone reading through the online conversation that is undecided on the issue, someone who is not sure which side of the debate they are on. They will hear your reasonable and rational comments, compare them with the aggressive words of a pro-captivity supporter, and it might make the choice of the undecided a little clearer.