Tonight I was denied the jumpseat on an NWA 757, 1/2 full, last flight of the night, because of where I am employeed. Because of this and recent events, and the disrespect towards my fellow employees displayed over the last 15-18 months...many of whom are furloughed from an ALPA carrier, some of whom are furloughed from this ALPA carrier, I will no longer accept an NWA employee on my jumpseat.