Well, I think the problem is that it is an unnecessary compliment.
Kamala Harris may not want people to believe that her looks contributed to her attaining the position of power that she now has.
At the end of the day, before, she was just a name on a piece of paper. We had no reason to believe that she had attained her job through means, other than hard work.
Now, there are a few feminists that will be in arms and taking about it reinforcing the secondary status of women and etc. However, obviously, that is off the mark.