The reason I chose those statistics to quote was because they were the only ones for which a direct comparison from the same source was possible, thus we can assume that the two figures are using the same definition of bullying (some may include minor teasing or avoidance, others may only consider outright insults, etc.). I highlighted the discrepancy between the two sources to show why a direct comparison is impossible without more information.
They won't be nearly so quick to criticize as when their fellow student is themselves homosexual.
Another thing we need to keep in mind when reading these statistics is subjective bias of the respondents. For example, I don't know how many times growing up I heard someone say "you're such a fag", or "that's gay" or something similar (in the same way as they might say "you're such a loser" or "that sucks", without actually intending to refer to sexuality, losing at a particular activity or whatever). As a straight white male, I never thought twice about people using such an expression, and would never have claimed to have been bullied just because someone said I was a fag. A homosexual student on the other hand, if called a fag would be far more likely to take that as bullying, and, in particular, as bullying because of the fact that they are homosexual.
Without a consistent (and explained) definition of what they are considering bullying, what they are considering homophobic bullying, etc. between studies, any comparison is pointless. Further, because of the subjectiveness I just explained, you can't extrapolate from homosexual students to students with homosexual parents.
I'm not saying that your argument is wrong, just that you haven't yet presented data which supports it. I fully agree that, if it can be shown that being raised by same-sex parents is more detrimental for the children than the alternatives (foster care), then it should not be permitted. I haven't yet seen any good argument that this is the case.