the person who hates their own gender has unresolved issues with someone(s) in their life (or in their history). those issues could even be self-loathing, and lack of acceptance of themselves too.
i would say that it might not make them unsuitable completely as a partner, but will come up again, and should be addressed (or at least understood). i actually think those issues have less bearing on their lives if they are aware of them, the source, and can then compensate, and work on them.
we all have baggage, and issues. and i'm not sure where this falls on the scale of risk or detriment. but i still think we should want partners who are more self aware and eager to address these kinds of things, simply because they will translate into other areas, such as when raising children.
a woman who has issues with other women will possibly raise a daughter, projecting messages that might not be helpful, mistrustful. a father can raise a daughter who might be taught to trust no man, and be skeptical about every guy she meets, etc.