Yes, and I can choose to not involve you in the political demonstration I'll take part in. Worst case I can cut of contact with you entirely, if I don't trust y

Yes, and I can choose to not involve you in the political demonstration I'll take part in. Worst case I can cut of contact with you entirely, if I don't trust you. But removing shared DNA is not possible. I'd have no recourse against you giving an uprising authoritarian government the means to identify me.