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.