Anything can be spam because spam is in the eye of the beholder, but nonetheless, politics is generally not spam. You can have a politically-neutral policy against undesirable content that passes the smell test. It does require that you a) use reasonably objective terms in the definition of "spam", and b) that you resist the inevitable pressure to reinterpret those terms to cover that which others find undesirable political content.
Actually politics generally is spam - in the sense that much of it is knowingly dishonest self-promotion of individuals and social groups.
Just because politics isn't trying to sell you a penis extension doesn't mean it isn't trying to sell you something far worse.
It doesn't even matter how political content is published. What matters is that currently voters get more protection from a faulty toaster than from lies knowingly generated by politicians and corporate PR outfits.
The creation of deliberately false "talking points", fake news, smear campaigns, organised trolling and astroturfing, fake reviews, fake feedback, and other kinds of cognitive pollution should be banned from all forms of media.
Which is not to say this is easy or straightforward. But attempts should be made - because lying to voters and consumers is absolutely toxic to genuine democracy.
Both are messages coming to you. Just because they have the right to metaphorically knock on your door doesn't mean both campaigners and vacuum cleaner salesmen don't get the door slammed on them and doormen won't tell both to scram if they try to visit apartments unsolicited. The difference in categort broadness seems classically strawmen as well.
