Diseases of all kinds can be transmitted through sexual intercourse, no matter their sex. Despite the fact that pregnancy would not result from unprotected sex, homosexuality is not immune to disease transmissions.
As for the safe part, I am not quite sure what it is referring to, but aside from possible disease transmissions, I can say it is....Safe? But definitely not safer and healthier than heterosexuality than heterosexuality is to homosexuality.
This is the epitome of a loaded question. Is homosexuality "more generally healthy and safe"? Healthier and safer than what, exactly? We are left to assume the asker meant in comparison to heterosexuality and by that, of course the answer is no. High risk sexual behavior isn't linked to orientation, anyone -- gay, straight, bisexual, asexual -- is capable of making poor choices in the heat of the moment. When common sense is applied, some people are healthier and safer than others.
There are diseases that are found with homosexuality, such as AIDS. Homosexuality is not healthy or safe because many of these diseases cannot be cured, and a person may not live long with a disease such as AIDS. Although these diseases can not be spread with solely being around someone, they can be passed when blood is passed through open cuts or wounds, which could happen.