This isn't actually what they're saying. They're saying that people apply a double standard to flawed and unlikeable characters based on their gender. And I think that denying that that is at least somewhat true, even for people who are otherwise quite normal rational people, is to fly right into the face of reality.
I think Adam, Ray, and Charlie are also flawed and unlikeable. I just never have to see them being flawed and unlikeable alone, for entire episodes. I couldn't take a show with nothing but Adam's psychotics, Ray's self loathing, or Charlie's whipped doucheness. They are all one-note and only work together.
Hannah gets the ire because she is the only one we get forced alone time with, and she is the vessel for the show runner. So she isn't just the character. She is the creator, writer, actor, and character. Therefor any dislike will pile on. It's fair. If we dislike the others, if they annoy us, the entirety of the blame cannot fall on them.
If you can give an example of a comparable situation where a male created a character for a show, wrote the character, acted the character, and said character was equally flawed and unlikeable please present the example. I can't think of one. Keep in mind that real people are flawed, and striking that balance for television is difficult, but when done right can be quite endearing. People like flawed but redeemable characters. It's relatable.
Again, I don't like any of the characters on this show. At least I can say I would never choose to spend time with them if presented that option in the real world. So, gender isn't at play here. There is just one of them that I see more than the others, and she also happens to be the one in charge of making sure that happens. I consider the criticism fair, and I'd complain about watching a show that focused heavily on any of the other characters, male or female.
Do you like and relate to every single person you know? If you do you're either a saint living among saints or you live in a bubble of familiarity.
It's OK not to like Hannah. Some people we just don't like. That's how life works. Hannah's "unlikeability" is being brought up as an argument against the show, though. And it's a bad argument. Add to that all the "Adam is cool" opinions and I cannot find a single reason for that disparity other than gender.
Adam isn't cool. He's more entertaining than Hannah (on television -- in reality might be another story) and it was enjoyable watching the interplay when it was him and Hannah together. The overwhelming dysfunction was interesting on camera. But make no mistake, he is quickly proving himself to be a total psychopath.
They both have their moments where their flaws/unlikeableness are fun to watch, but too much of either would get old quickly for me.