Traders are hardly just on Soulseek. Most probably aren’t since it’s so accessible. Most of the traders I’ve seen on Soulseek anyways are scammers who are just sharing RED repositories. Or they’re on dc++ hubs where you can’t have locked files anyways

The best thing good users can do is remain on the client for the long term, ensuring traders remain a small minority. The next best thing they can do is PM traders regularly with requests to share. Make their sessions a pain in the butt due to the private chat alert going off routinely. 'Hey trader, please open up to non-buddies temporarily, even at a crippled speed. I'd like two items from you. You know Soulseek is a sharing platform, right?' Some may realise the ridiculousness of their position and co-operate.

Don't stoop to their level by blacklisting, either. They will take that as endorsement of their behaviour. (Set 20kb/s down if it makes you feel better.)