The demand for more diversity in games tends to have a counter-reaction sometimes when diverse characters of race or gender are added to said game. These new characters "aren't how we imagined they should be" or "that's not how X and Y should look, or act" etc...
Not just in Halo, and it's actually a lot milder in Halo, but in other mediums as well, you'll find a lot of hostile opinion over characters that don't meet the very rigid standards that people erect for them right off the cuff.
A good critique would be in 2 or 3 games from now, when we can take a look at Palmer's character arc in a more contextual way, and see how much she has either grown, or hasn't. There are valid things to judge once a character has been around for a bit.
And not every character is meant to be likable anyway. Some characters are polarizing. That's what makes a good sci-fi story, when you have all sorts of people, working in tandem and from different angles, admidst galactic chaos. She may come around for the gamers that hate her. She may not. But she's there for a reason, and that is something to be expounded upon down the road, so I'm totally fine with giving her the benefit of the doubt for now.
