In modern Africa, there's quite a large undercurrent of thought that states that "homosexuality is unAfrican," despite the fact that many traditional African cultures do include homosexuality and do acknowledge and celebrate homosexuality as a thing that people can be. However, I'm having trouble finding information as to whether or not there were homophobic sentiments in traditional African societies pre-colonisation. Was homophobia imported from Europe? What form did it take in Africa, if any?
As kind of a counter-question, or rather a request for clarification, I want to point out that what we, in the West, might define as homosexual behavior might have a completely different context in another culture. Male-on-male sexual behavior has a very different meaning if it's a religious custom (as with the famous example of the culture that believes it is necessary for boys to ingest semen).
In labeling sexual acts between members of the same sex as "homosexuality," do you think we run the risk of projecting Eurocentric ideas about sexuality onto non-European people? Have you read about African cultures that feature homosexuality as we define it, as opposed to, say, ritualized sexual behavior or redefinitions of gender/sexuality as part of a religious belief system? And would those still count as broader examples of homosexuality, or as something else? What examples do you have in mind as celebrations of homosexuality?
Short answer: yes and no. Yes, in that some (certainly not all) actions and desires that would now be labelled "homosexual" were stigmatized in some (again, not all) parts of precolonial Africa. No, in that no one thought about these actions and desires as constituting an identity in the way that most people in the modern west now do, and the stigmatisation of homosexuality as an identity is substantially a product of the colonial encounter.
For the long answer, look up Marc Epprecht's work, particularly the book Heterosexual Africa?.