How do I as a Master tier subscriber turn off content sharing in a campaign I'm not the DM for.

I want to turn of the content sharing for some of my purchased adventures in a campaign I'm a player for. It seems that only the person who created the campaign can enable content sharing. I don't want the ppl I personally don't know have access to all the adventures ive purchased

Content Sharing is enabled or disabled by any player with a master tier. 

If you have not enabled it but content is still being shared then somebody else has a master tier and has it enabled.

There is no way to prevent sharing if somebody else has enabled it. But, given that it has no negative effect for you in any way whatsoever I'm not sure why you'd care. 

The other guy has a Master teir subscription and has enabled it. In the campaigns I DM the adventure is blocked, and that is my choice, come to this campaign snd someone else who doesnt contribute anything uses material ive purchased to run a game, when I don't know them from Adam.

But them using it doesn't result in anything negative to you. Who cares if they're benefiting? Why does it matter? If you don't like it and it bothers you for some reason then find a different campaign. 

Could not you just make a new account, but do not buy anything on it, and then join the campaign? It is more of a hassle to create a new account in my opinion, but at least you are not contributing anything.