Especially if you signed up for something, rather than just unsubscribing marking it as spam is a dickish move given that it has the potential of that mail also being filtered for people wanting to receive it.
If you don't want that you'll have to make your marketing emails opt-in instead of opt-out after signup is complete. If I have to disable a ton of auto-enabled marketing options on every page, you deserve to be listed as spammer.