There is a subtle but important distinction between saying "We support your cause but the amount of money we can afford to spend advertising our cause depends on how much you donate" and "If you donate money we will support your cause, otherwise we are supporting the other side."

A PR firm supports anybody who can afford to pay them, no matter the cause. A political lobbying group supports causes based on their political beliefs and accept donations to support those causes. In practice, many groups are a bit of both, and many PR firms try to look like a political movement because it's more respectable and they have more power. The ACU just let out that they lean more towards the PR end of the spectrum then the actual political movement end.

Jay