Operators can run their campaigns however they want as long as they're within the rules of the forum, but I think things like this should be stated upfront as part of the terms of the campaign if it's an issue but I don't think users should be expected to refrain from promoting competitors without warning. I can see from the operators perspective why they wouldn't want this just like if you were advertising for Pepsi they wouldn't want you advertising for Coca Cola or promoting any other drinks but this would all be laid out in their contract and I think it should be the same here and made part of their rules if it's something they don't want. Rather than recommending the product they're advertising they should probably just refrain from posting on the subject if they can't remain impartial under the terms of their campaign, which is what I would do in this situation.
I agree with everything in your post...I think that the first statement is generally a little bit blurred though. Are there any specific rules for operators? Can they threaten campaign positions for content that is not actually dangerous to anyone, just like the OP? It seems like it's a (potentially dangerous) moot point.
Honesty is the best policy. The moment that honesty is being compromised as a result of the signature campaign, is the moment that the forum can be considered corrupted in some way.
One might say "well, then people like the OP should not participate in a signature campaign" - though that would be penalizing an honest member who is not harming anyone...and that would mean that everyone within the signature campaign would have to refrain from being honest or compromise their honesty if they have an opinion outside of the operator or campaign managers interests.
Forums are for honest discussions. We should not be entertaining icopress's behaviour if we want to preserve integrity here in this forum.