I can tell you that we should prevent mamzeirus from happening; I can tell you what caused a certain historical case of mamzeirus to have occurred; but I don’t know if I can tell you what to do about a mamzer that has already been born.
The gemora talks about mamzeirum that were talmidei chachomim. So we should treat them with respect. It isn’t their fault but rather their parents fault. But they are still a mamzer.