"Our field is open to anyone (ie. Local Club Members, AMA members, newbies, crack-heads, etc.). "

That's the problem...

If the field is truely open to anyone, then those non-club/non-AMA members can spoil it for everyone.

Our field has big signs stating that it can ONLY be used by AMA/Club Members, and there are several large signs stating usage rules.

In addition there is signage stipulating flying areas and prohibitions on non-club members entering anything other than designated viewing zones.

If you can get the club to put up similiar signage, and get before those who may be involved in trying to close the field down to express your intent, you may be able to save the field.

But you need to convince them that Club/AMA members would never behave that way, and that restriction and statement of usage, rules would eliminate the possibility of violations by non-club members.

Our club field has a gate that can only be opened by club members. Club members can and will ask people to observe the rules.
The police also makes rounds to check that there are no problems with unknown "guests".