The asshole thing is probably not just an act.
Definitely not a junior member of staff.
Deeply offensive to any Irish person coming from that guy.
But the the big dumb ass getting himself into trouble is funny.
Conservatives can enjoy Clarkson because he backs up their belief system and his humour is based around taking that belief system to humorous extremes. Lefties can enjoy Clarkson because he comes across like an exaggerated caricature of a conservative.
It's like an inverted version of American conservatives enjoying Stephen Colbert despite his character being a liberal caricature of a conservative. Clarkson's actual beliefs are ambiguous though. I'm not sure that there's any real ideology behind anything he says - he's a shrewd man and his persona has always been based around being outrageous.