Are you part of an apolitical constitutional monarchy or are you a common citizen who should have to work for a living?
At the moment you are neither.
If you are the former, then smile, hold your views and let the elected representatives of the people and their duly selected officials do their job. Go to York and do "duke" things. For all of their many many faults, they have more authority than you do. You have had a reasonably notable military career and have an honorary role going to meetings for the Department of Trade and Industry.
If you want to get into politics, then distance yourself completely from your mother and brother, and go on - but don't expect to have any taxpayer funded privileges that come from your title. I am not saying you are wrong, I am simply saying you should not use your position of constitutional privilege to criticise the duly elected government or engage in foreign policy without its explicit permission.