Well I am not sure what in GR caused people to get angry? Engineering appears sound, measurements are good, adjustable sub section is a good thing, speakers go down to 20 almost flat, Danny improves and upgrades speakers from big names and people seem happy with his work.
Big names employ engineers like him. And after all, Tesla also was small shop installing batteries into Lotus frames... Linus started alone and almost dethroned huge names in operating systems with Linux...
a) Several Agon guys are dealers (or pied pipers who work for such dealers) throwing names of things they sell at ya. GR is a manufacturer direct brand. Hence, no dealer middleman around here is making any cash if you bought a GR speaker. You will note similar levels of animosity on display for other manufacturer direct brands as well.
b) GR’s speaker upgrades (of other brands) tends to expose a lot of design flaws, excessive corner cutting, etc in name brands that these dealers tend to carry. When their sales dive downwards a bit thereafter (understandably), they have historically been mad at GR instead of telling their goofball speaker designer to get his act together.
To summarize, GR is a bit of a double whammy disruptor. Hence, the dealers association around here tends to hate him a bit.