I do not see the connection between this law, which is similar to many other laws all over the planet, and homosexuals, regardless of the beliefs of the governor of Tokyo.  To go back to what the law is described as (assuming this translation/summary is trustworthy, and it seems to be):

Quote - Now the criteria will be expanded to include: “Any manga, animation, or pictures (but not including real life pictures or footage) that features either sexual or pseudo sexual acts that would be illegal in real life, or sexual or pseudo sexual acts between close relatives whose marriage would be illegal*, where such depictions and / or presentations unjustifiably glorify or exaggerate the activity.”

This is pretty specific language and I don't see how you're making the connection to an anti-gay agenda.  Is it illegal to be gay in Japan?  That's a serious question since there are mostly-obsolete anti-sodomy laws in the US.

My Freebies