Not true. It's trivial to spread immorality and normalize it which would lead to risky sexual behavior. We're literally living through it now. Just look at how things slid in the past 100 years on that front.
People who engage in risky sexual behavior increase the spread of STDs in the population as a whole, causing increased risk even for those who don't engage in risky sexual behavior. The parallels to COVID seem pretty clear, no?