As requested, I am reposting this to a new thread. I edited the excessive introduction and conclusion.
Here are some ideas which may help future advocacy work end up with more people wanting to agree with a position. Please keep in mind that I am not a politician or a political advocate, what I am saying is based in my knowledge of social pragmatics skills and remediating those skills in adults with acquired neurological disorders and children on the autism spectrum. Professional politicians and advocates probably have much more refined knowledge and I would defer to them regarding specific advocacy advice.
1. If you're a member of an organisation disclose it immediately, especially if it's a formally incorporated organisation. Your organisation is something to be proud of! You do advocacy through it, provide education, establish industry standards and practices, and hopefully fund science. Your mindset should be that your opinion is valuable *because* of your affiliation, not *despite* it!
2. Tone your posts as a discussion instead of an argument. If someone says "the FDA found X chemical in e-cigs" then instead of replying "you're wrong because X chemical was in only one cart, do your research", you might try "hey thanks for pointing that out, I went to their website and read their report and it looks like it was only in one cart, here's the links I used do you have any more information so we can keep getting to the bottom of this?". See how the first statement sets up the two people in opposition, whereas the second one sets them up as allies working together? It's much easier to convince an ally than an opponent.
3. If someone makes a valid point, don't try to explain it away. Rational people are willing to accept the world as imperfect, they'll accept some flaws with PVs. When people say "there aren't enough studies showing it's safe", instead of saying "it's gotta be safer than tobacco" try something like "you're right, and that's why we are gathering money to do more tests/have a letter writing campaign to the manufacturers asking them to do more testing". Treat this as an opportunity to find a place of agreement and assuage their concerns, from there you can work towards other places of agreement.
4. Avoid putting words into people's mouths and turning their narrow statement into a broad statement. If I said "It contains chemical X which is found in antifreeze." and the reply was "So you are for a total ban of all salami because it's in that too?" I would immediately be angry and defensive because that is not whatsoever what I said or meant. Know your goal. If you're doing advocacy that goal should be to win people's support, not to win arguments against them.
5. If one person has already responded to someone's points, don't jump on the bandwagon. No one likes being ganged up on and the probability of two people settling a disagreement is much higher than 1 person settling a disagreement with what they perceive as a mob of attackers. If you really feel you have a point then send it via PM to the person you think needs help in explaining their side. What's more important, that you get to say your piece or that the cause you're fighting for wins support?
6. If you cannot end with an agreement, at least end on a conciliatory note. Something like "it just doesn't look like we can see eye to eye on this right now, maybe if we both go and do more research we can find information which helps us agree" at least leaves things open, and even though the chances are that you'll never end up agreeing it looks a lot better to people reading the thread than "you're a ....., I'm done talking to you!". Having people think "wow, that guy is a jerk" doesn't motivate them to go learn more, and much of the time the people you impact are not the ones replying to the thread.
7. Don't insult, belittle, dismiss, condescend to, ridicule or otherwise mistreat people. Spend a minute in the other guy's shoes, how would you feel if someone said what you're about to say to them to you? Would you want to be called (or have it inferred that you are) ignorant, stupid, uneducated, valueless, childish, etc. Regardless of the fact that it is incredibly rude, it will definitely close people's minds and lose any chance that they will see your side of an issue.
8. Finally, remember that you're walking into someone else's house when you post in a forum. Be respectful of their rules and accept it if they say that something isn't welcome.
If you want to sum all this up into one easy to remember idea, it's that doing advocacy work is making friends. When the person you talked to goes to vote on the cause you advocate, you want them to think "I don't want my friend to lose". They need to feel personally connected to your cause and they get that by feeling personally connected to you.