Crossing the border undocumented and beating up innocent people in the street is illegal too but yet goes unpunished in the west now, so using BTC is fine.
If you want to really be pissed off about high level illegal shit watch "Dirty Money" on Netflix. Something like 12 episodes about an hour long each. Each detailing stories dealing in billions of dollars. There is even a specific episode for
GOLD (you know... that other asset that the government seems to like)