If saying climate change is real could be seen as partisan activity just because some candidate or other denies it, then surely the same would apply to all advertising for, say, Coke or Pepsi if some candidate expressed a preference and intent to favour one or the other (esp. if in government contracts) – or more realistically, if some politician spoke out against the widespread marketing of both these and other similarly poisonous addictive beverages.
Perhaps having to report their advertising budgets as third party political advocacy would not be too much of a burden on the big soft drink companies, but they would not be the only ones so labelled, and the loss of charitable status for healthy food advocates would be a nasty consequence of having their cause taken up more by some politicians than others.
So, if this interpretation stands then clearly the legislation was incompetently written. But perhaps the real takeaway is that all charitable contributions should be no more eligible for tax deduction than political ones. A fixed per person limit would both reduce the window for scammy self-serving “donations” and provide less encouragement for the wealthy to distort our pattern of social service by giving massively greater support to those charities that they happen to approve of.