Being a Methodist, and having read their literature and news and attended their services, I can confirm what you are stating. Like many Christian denominations today, the Methodists seem to have adopted a left-wing, extreme liberal political aganda in place of the proper funtion of church, i.e. to lead its members to live better lives in keeping with Christ, and to obtain salvation.
Guns are merely ONE problem with Methodists today. The Methodist church supports gay rights, opposes drilling on the north slope of Alaska, supports the INternational Congress on Racism which Bush correctly refused to support, etc., etc.
Your suggestion about complaining is a good one, but personally, I feel the only real solution is to remove from policy making positions in these churches those leftist, socialist clergymen who support this type of agenda. They are unlikely to respond to complaints, opinion or withdrawal of funding.
I've clearly been ignorant of the leftist leanings of the UMC, I was floored as I read the 2000 Resolutions. I can't imagine rank and file Methodists would support such an outright betrayal of individual liberty. Spiritual support of an agenda is bad enough, but to think that the money I've given the church - blissfully unaware of the Home Office's views as I worshipped in Texas - is being used in support of yahoos like "The Center To Prevent Gun Violence" is truly disturbing.
I ask this as a sincere question: Why do you stay in the Methodist denomination when there are other, larger denominations that are not opposed to our God-endowed liberty? Voting with your feet, as it were.
Terminating these people from employment in the church would be harder than getting rid of a worthless union member. It would be best to achieve change through membership withdrawl.