In addition to promoting your own ideas, you should also be trying to slip poison into your enemy's pool of ideas. And by "poison" I mean ideas that:
>Your enemies would find agreeable
>Are backed up with dubious evidence
>Look ridiculous to moderates and neutrals
You want enough of your enemies to believe these ideas, so that neutrals will look at them and be turned away.
We'll use the concept of false flags as an example. Every time a white guy does something horrible and it makes the news, people on /pol/ start claiming that the incident was just a false flag done just to get people to hate whites. The criminal was paid, he was a mind-control patsy, it didn't really happen, etc. Neutrals looking at /pol/ are going to think "holy shit, these guys are insane" and be dissuaded.
Now imagine if it was your enemy thinking that. Imagine if, next time a Muslim shoots up a building, you had people all over Tumblr and Twitter picking apart every bit of information about the incident, desperately searching for and compiling evidence that the shooter was a paid agent or something to make Muslims look bad. People on their side might believe it, if there's enough "evidence". But neutrals would just look at them, think "these guys are insane," and turn away.
The idea here, essentially, is to create a controlled opposition of sorts. Inject crazy ideas into their overall pool of ideas, and play them up to drown out their more rational and convincing ideas. But of course, we don't have mole accounts with thousands of Tumblr/Twitter followers; otherwise, we could just use our influence to make them look as ridiculous as we want them to. Instead, we'll have to work the old meme magic to slowly slip the poison into their pool of ideas. The more poison we slip in, the harder it is for neutrals and moderates to take your enemy seriously.
Of course, it is possible for prominent voices on the enemy's side to counteract memetic poison. They may or may not be aware that their side is being poisoned, but they'll do whatever they can to fight it: elevate the rational and convincing ideas above the ridiculous ones, denounce the people who believe the ridiculous ones (this might cause infighting!), etc. Be cautious of them, and find ways to prevent them from counterattacking.