Any statistics to backup this quote?
I have no idear which percentage of the tx are for illegal purposes, but i've been part of the community for ~6 years, and my gut feeling tells me it's the other way around (>95% legit, <5% illegal). But, like your post, i don't have actual statics to back up my claim (just my gut feeling).

The problem here is that the mainstream media only reports on the bad aspects of crypto. They don't care if newegg adopts bitcoin, or if bitgild sells a ton of gold, or if binance exchanges millions from KYC'ed people, if bob pays alice for some artwork, if UNICEF receives tons on crypto donations,... . But if a ransomware asks for $30.000 to unlock a company's server, they jump in and make it look like crypto currencies are only used for illegal purposes.
Mainstream media thrives on negative reports, especially if it marginalizes a small group of people. It's beneficial for them, they can scare people about a technology they do not use, it makes their readers feel good about themselves and scared about crypto, and it makes them buy newspaper subscriptions.

But, if you've only read mainstream media, i'm pretty sure you'll end up with the belief most of cryptospace is filled with illegal things,... But it isn't. These are real people, and just like in "normal" society, most of them are good folks, but a small percentage is bad. It doesn't matter of these bad players use crypto or fiat to conduct bad transactions tough...

As for the fact you reported a scam ring: the only thing i can say is "kudos". It doesn't matter if somebody is stealing fiat, crypto or physical items,... Thiefs and scammers should be stopped and reported, and i sincerely hope they'll catch these guys.