Unpopular opinion: don't have sex with random people and you wont get STI's.
Notice how STDs were far far less prevalent in the past than they are today, and far less prevalent in countries with a healthier attitude on relationships and sex.
To your example specifically: don’t cheat either? Are you implying that “people cheat on each other, so there should be no moral standards”?
https://wisevoter.com/country-rankings/std-rates-by-country/...
For some STIs the main consequence is the stigma in the first place. Creating more stigma to reduce
I'm busy at work and OP is probably not going to change their mind, so I'm leaving this.