I think the main problem is the false claims (aka lies), not the coloured gear, not the personal preference that divers from "true to the source". And to cover up the false claims, they are anti-measuring objectivly.
Not all are like that. A good example is Nelson Pass. He don't claim clean sound or the best technical advanced designs, he says himself his amps are mainly about adding harmonic distortion to the sound to make the sound sound "better" while still being reliable. That "better" is off course subjective to his standards, but it seems he got a point for a small part of the market. His designs are not secret, as he shares a lot (not actual versions, but almost all old designs) to the diy world and explains how they work and why what and how. He also is clear about the pricing, he asks the big prices for his Pass Labs brand because he can (Pass Labs sales are good). But also designs amps for smaller budgets (First Watt a.o.) or just free open source designs (on diyaudio.com) as it's his hobby. Off course that is also good advertising for his main brand, but most of his diy followers won't have the money to afford those i think...
But most are not like that. They like to hide their claims in a most of audomyths and wooh, while their designs don't do what they claim. That is the big problem.