Don’t try to reason with a person who does not understand pathogens that are to small to see with the naked eye. You will not get anywhere. Find another reason why they need to embrace sanitation. This could be smell, safety from molestation, privacy, etc.
If everyone in a village does not use safe sanitation then the pathogens in feces from the person that is not practicing safe sanitation will affect everyone and the benefits will be minimal.
In many societies the inhabitants will say “yes” to any question you may have. Verify that the person you are talking to really means “yes” to your questions.
Don’t get fixated on a certain sanitation system. Analyze what the population needs and provide the most sanitary system that the people will use and maintain. Better systems can be implemented later as the population accept and embrace what you have provided. You have to gain trust.
When working with local populations identify the leaders and decision makers. Work with them since they will be able to influence the rest of the village.
Sex can make a big difference in how you are accepted. Having the same sex working with people is usually easier. Having women working with women and men working with men is usually easier to gain acceptance and trust.