For the marriage of Aisha, there is no hadith that suggests that she was married at the age of 6-7. Marriages for the daughters were considered a way to make relations between families stronger, and that is for business reasons. They used to choose who will their daughters marry since she is first born. But that was not the case with the prophet. What happened when she was 6-7 years is that her parents and the prophet talked about it and when she became ready (age) she gave her acceptance.
There are many hadith talking about the age of Aisha, but it is not a concern for me to really know the age. This is because that issue only emerged lately meaning that it was completely accepted. Second, the only sources to know the age of Aisha is her narrations and hadith and she is the biggest Islamic scholar. If one looks into these hadiths, we notice how happy she was and how she describes the prophet, her life, and their relation. And there is nothing more authentic than her saying that " I witness there is no deity except Allah and that Muhammad is his messenger". So this disproves any thing claimed about the prophet peace be upon him regarding that issue.
I would advise to read the biography of the prophet peace be upon him before jumping to conclusions. We can't sit here and judge things that took place 1400 years ago without knowing some background information. If one thinks that he has it all covered, than think again and go verify.