My karma is my action or behaviour. How I tend to act, have acted and still act. Karma matters because actions have consequences. I realise that my actions have been unwise and uncompassionate and accept a responsibility to "cleanse my karma" by acting in accordance with meditative insights. However, not all karma is mine. Each of us survives early childhood only because of the actions of adults. We are fed, taught and socialised. I was also indoctrinated, pressured, bullied and intimidated. Many of my actions were reactions to theirs. Thus, I tended to be solitary and resented being condemned as unsociable.
I cannot cleanse the karma of others. Bodhisattvas act for the enlightenment of all living beings but most living beings will not noticeably approach the realisation of their enlightenment in our life times. Politics addresses action collectively, not individually. We struggle to build an association for the free development of each. Thus, each will be responsible for his own actions but will not be impeded, indoctrinated or intimidated by the actions of others. This is probably as much as we can do to address the fact that many of our problems are caused by the actions of others.