Your post is oddly worded - are you posting with Google Translate? What is 'the sex world/place'?
I find punters generally have more sense than to get personally attached with somebody they're buying a service from, just as I'm not personally attached to my hairdresser
. As with any other inappropriate behaviour, if they push it then they're no longer customers.
To avoid the majority of STIs, don't offer unprotected services. To avoid them all, don't have sex (which does mean you can offer something very low risk like massage with HR - there are threads here about it).