If you're already a cogent customer, you're unlikely to drop Cogent because they spam. There's costs and risks associated with onboarding new transits, and (one of) your current providers being spammy to other people isn't generally likely to drive a business decision.

If you're not a cogent customer, you're either not going to become one because of their tactics, or you are going to become one because of their tactics. I guess it's working towards the latter given how long it's been going on for.