It is not discriminatory to choose not to have sex with someone with an incurable communicable disease. It's every person's right to make their own choice. In point of fact, by not sharing such important information prior to beginning a sexual relationship with someone takes away their choice and calls into question the trustworthiness of the partner withholding information. If they would fail to tell me this, can I trust them to let me know when an outbreak is starting to alert me to the increased possibility of becoming infected? Claiming discrimination is an invalid argument. Yes, some people will make uninformed choices, but that does not entitle the person with the disease to prevent their partner from making an informed decision. Period.
In answer to the original question, you can't make him see the danger posed by others. You can however talk to him about the warning signs, set up boundaries for specific behaviors (no asking that he leaves you, for instance), and request that he not share with you spoken opinions about you. It would be soooo nice if he chose to defend you, but that might not be his personality, or he may feel she is only venting. Regardless, there is no need for you to be hurt by it. I am very sorry you've had to deal with this, and I really feel for you.