You don't like the site so you want to remove your ads from it. Wouldn't it be better to put ads so their readers can go to your site and plead to them there?
Put ads on breitbart? You seem to be very much missing the point.
Edit to add:
Even if you believed, for some reason, that you could usefully engage the readers of that site, giving money to an organization whose goal is to spread beliefs that are apparently abhorrent to you would be a questionable plan. At the same time as you would be spending money to promote your beliefs, you are funding the opposition.
I think you'd need to provide some evidence that by commercially funding a view you really don't like, support for that view is reduced. I would expect the opposite to be the case. Why do you think it would work?
I'm not particularly well informed on the actual logistics of mounting a secession from the rest of the US, although at the very least I would imagine securing water rights would itself be a significant challenge for SV, but I very much doubt the "disruptors" in SV have the wherewithal to stomach such an endeavor.
I'm not super familiar with the geography there but I'd imagine everything west of the rockies (is that the right mountain range) would go with California and I thought that this was the source of the water.
I believe a large part of Northern California's, and by extension Silicon Valley's, water comes from the Sierras. The communities of the Sierras, as well as those of the Central Valley which separates Northern and Southern California, tend to be fairly conservative. They also have high rates of firearms ownership. I don't think they would be too keen to join in on a hypothetical SV secession.