He's using "gay" in its normal form there. PDP has said a lot of shitty things, this isn't one of them. Light's sexuality is ambiguous because he's such a manipulative asshole in the series that you can't actually take any of his relationships at face value. Some read into this and think he's gay/asexual/etc. because of it. (but it's a stretch, it's more a big ??? because it's not relevant to the story.)
Damn right it's not relevant. Not once is his sexual nature even hinted at, so assuming he's gay says more about the viewer than the actual source material. This is actually the first time I've heard anyone refer to Light as gay, which wouldn't be a problem except that it's a completely baseless claim. While I don't think this is necessarily a shitty thing to say, it does speak to PDP's overly simplistic yet aggressive and uneducated perspective.