The point is that it is hypocritical for one group of employees who enjoy a certain standard of t&cs to negotiate t&cs for another group of employees on lesser t&cs.
What, you mean BASSA? LH CSD's who hardly ever fly, creaming off the subs for 'union days' standing idly by while the regions get closed down and LGW gets squeezed and squeezed?! Come off it!! It's about integrity. Whether it's MP's or unions or anyone else who stands to represent others, of course one can represent a group of which you are not a member if you are chosen to do so. Show a lack of integrity, then sooner or later, you will be found out.