Yes but who is going to believe that after hearing so many other drugs will ruin their lives then finding out they don't?

The opioid crisis isn't related to the war on drugs. It was caused by doctors being misinformed about how prescription opioids worked by the drug manufacturers + widely disseminated (funded) research about pain treatment. This caused people to be prescribed opioids without a risk assessment for addiction or similar, and thereby lots of people got addicted after being prescribed for broken bones, surgeries, and general discomforts.

When you hear about X overdoses in an area in a shockingly small amount of time, it's not people dying because they took too many oxycodone pills, it's because of street fentanyl. You can thank the war on drugs for that.

I suspect it was meant as a: "They told me marijuana would ruin my life, but after smoking some, my life is fine, so surely they lied about the other drugs as well"

TL;DR: Marihuana not as bad as stated, surely fentanyl is fine too.