The reason he is abrasive is that he has been arguing the same things for 30 years and people still keep coming back at him with the same irrational stuff. He's only human,so I think he has a right to be a little bit pissed off.
Homeopathy - right. There's medicine, and then there's stuff which doesn't work. If it's medicine, it will have been trialled and monitored in carefully-controlled conditions designed to eliminate random outside factors.
Something changes when "alternative" medicine starts to show evidence of working - by which I mean proper, researched, peer-reviewed, demonstrable carefully-logged evidence that it is effective more often than it is effective (and not just "it worked for me", because there are hundreds of other factors which could come into play there, e.g. the placebo effect which Kathy mentions).
What happens is that then it ceases to be "alternative" and is just "medicine".
There's medicine, which works.
There's rubbish stuff, which doesn't work.
It's pretty simple.