The ability of people to believe in God, after not believing is amazing. It is not something that can be controlled. People believe as they are prompted by the Holy Ghost. It takes a certain amount of effort by the person, a willingness to learn, and the ability to trust the message being presented. For someone to trust the message, the truth has to be told. Trust requires feelings of love and acceptance. Love and acceptance is expressed by the person delivering the message.
When love and acceptance are not expressed, then the message is not trusted, and the whole discussion ‘goes south’. When the messenger has done anything untrustworthy, then the person hearing the message starts to wonder if anything that person says is true.
That is why integrity is so important for those who are sharing the gospel. For me to share what I have experienced, I must have integrity. I must be truthful, and trustworthy. Otherwise, anything that I say may be determined suspicious.
One example of someone who trusted the gospel message is in Alma 15. Zeezrom, who is a lawyer at first does not believe the message; but Alma and Amulek are so convincing, and have so much self-confidence that they catch Zeezrom in the lies that he has been telling. After he is caught, then he starts hearing to the message, and he eventually is converted and repents of his sins.