I saw that show. I'm betting it's because that UC was probably right there in the thick of all the crimes they were committing. It's the only way to get them to trust you. If you're prospecting and one of the patched members tells you to go stomp a mudhole in some dude's *** and take his wallet, you gotta go do that, or they'll stomp one in YOUR *** (if you're lucky), and you're out. You don't get the evidence you need by not doing what it takes to get into the club, after all, and you won't get anything on them until you're a patched member.
Are you suggesting that it is common practice for law enforcement to violate the law they are sworn to uphold in order to "get the bad guys off the street?" I find this idea ludicrous. The very idea that LEA's subscribe to the idea that the ends justify the means is pure poppycock. All evidence is gathered in a fashion completely in accordance with statute. To suggest otherwise, well, you may as well be a terrorist.