For me it is when companies/services market themselves as donating to XYZ cause if I buy their product. If they want to donate, they should have already done that with the money they have. Asking me to give them profit so that they can donate is so obviously pretentious.
If we used billboards for something like missing children or traffic announcements etc I’d be okay with that. But pretty much no actual ads for products. Billboards are a driving distraction and I don’t approve.