There is no evidence to suggest James Gunn is a child rapist. What there is evidence for is James Gunn making crass, gross jokes that leverage paedophilia for shock value. He is not alone in this behaviour nor exclusive, and we know this humour is generally leveraged by people attempting shock and appal their audience. It's a subset of humour. I've done it in the past. Many others have as well, utilising jokes where the punchline cites murder, rape, paedophilia, racism, or some other extremely controversial, counter-culture, politically incorrect trope or topic. I know a baby/fridge joke that I'd tell in my teens that I'm sure this version of Gunn would have found hilarious.
Gunn has since gone on record to discuss this brand of humour (again, let's identify that this style of humour is not exclusive to Gunn, did not originate with Gunn, is not propagated exclusively by Gunn), and how he has grown as a person since. Gunn's brand of humour dating back about a 8 - 10 years and his career trajectory revolved around deliberately gross, controversial jokes and punchlines aimed at unsettling people and stirring the pot. He openly discussed how he sees futility in this style of humour in his later years, the pointlessness of it all, and the obliviousness towards those who may be negatively impacted by it.
Not only recognising his actions and public image, he made several clear, conscious efforts to rectify his behaviour over the years. He has demonstrated himsefl as a person not only acknowledging and admitting of guilt to the humour he subjected people too and the potential ramifications of it, but growth as an individual to the betterment of his own audience.
The website you linked to is run by Mike Cernovich, a hard right nationalist and prominent supporter of Donald Trump and the Republican parties values (multiplied to extremetities). He actively opposes all forms of liberalism, feminism, and racial equality. He believes date rape does not exist (and is a rapist himself), and that there is an ongoing white race genocide that must be combated. He is a vocal mouthpiece for alt-right white nationalist values and ideologies.
Gunn has, for a very long time now, been an open advocate for the exact opposite values. He is pro equality, heavily liberal, and openly anti-Trump. It is not surprise that Cernovich penned a hit piece on Gunn, the latter representing the exact political opposition of ideologies he embodies.
Whether or not you or I or anybody else finds Gunn's decade old jokes funny or shocking is irrelevant to the claim that Gunn is a paedophile, of which Cernovich so brazingly parrots. Emotional outrage is not evidence. Ideologically fuelled hit pieces are not evidence. A fridge/baby joke cited years ago does not make me a paedophile. Doesn't make Gunn one either.