I am also an active member of a pressure group that sometimes stands in elections, if I were to be in any of these career choices while being a member (an active one, If I were on the internet/websites or well known generally) would I get kicked out of the jobs?
Journalist definitely not, not sure about the others. Civil Servants are not allowed to be politically active as they have to be neutral but I don't know if this applies to all state funded jobs (which RAF Officer and Teacher would be).
I think it's most likely that you wouldn't be, but it would be seen as highly unprofessional to make it obvious ie try and get colleagues to join the organisation or to take time off work to do things with it. Kept in your private life it is of course fine, but if in doubt, keep political views and jobs totally separate.