Why does it even matter about the legitimacy? Its kind of hard to argue for or against a point that has now current proof for or against it. And if it does, there is no proof on which both sides agree upon. It is just one never ending battle.
Horus was born under different circumstances really, I mean "born a virgin" isn't exactly what happened.
Isis and Osiris were Horus' parents, both god's in egyptian myth, which makes horus a god as well. There are paintings describing Isis and Osiris both "having sex" if you will, but its pretty easy to just say this:
Horus was a god, his parents were gods, and to be fair, there are no accounts of him being mortal so there isn't really a point in going "oh he's just like Jesus", because well.....he would have been born from a virgin god, child of two gods, and live only as a god.
Comparison to Jesus, who was supposedly born from a mortal woman, child of two mortals, and lived as a mortal(until rising up into heaven) its a completely different story.
TLDR : Comparing Horus to Jesus is pretty silly since they are entirely two different entities representing two different things with no real connection outside of people just saying such things for "popularity".
You were born by your mother and you were created by god because the first human (Adam) was created and wasn't born.
You speak the Bible as truth, written by politicians from thousands of years ago. There is actually proof of evolution and there is no evidence saying Holy Scriptures of any sort include truth, or as you may be aware of, science.