Not true. Homosexuality exists because it is was mandated by evolution, meaning evolution has dictated that a place for it exists. Its not a "problem" unique to human beings, either.

One of the psychiatrists I used to work for thinks that severe, organic mental illness like schizophrenia and bipolar disorder is also the result of evolution as it actually makes people seem sexually appealing to at least a portion of the population, albeit however small it may be. Homosexuality is likely the same thing as counterintuitive as it may sound -- it provides some value to the survival of the species, perhaps from a communal standpoint. If it didn't it wouldn't exist.

Its not like they are incapable of breeding. That would be an example of an actual problem.