If you were to compare a true medicine man to the likes of Lynn Andrews, the differences would be vast. The people who are claiming that she is lying are the very top eschelon of Native American culture, the Elders. They do not do this to "protect their secrets". Instead, it is of concern that non-natives are being misled by such people.
"We concern ourselves only with those people who use spiritual ceremonies with non-Indian people for profit. There are many things to be shared with the Four Colors of humanity in our common destiny as one with our Mother the Earth. It is this sharing that must be considered with great care by the Elders and the medicine people who carry the Sacred Trusts, so that no harm may come to people through ignorance and misuse of these powerful forces"--Elders from 11 Native American Tribal Nations
These Elders do not say such things out of prejudice. A Navajo elder once rescued me in a parking lot from harassment from another younger Navajo from a more remote section of the reservation, who was overly curious about me due to my eyes being green, my hair being blonde and probably being the whitest white person he ever saw. He didn't have to come to my aid but he did and made sure that my son and I were alright. From all that I've heard and my own experience directly with an Elder, these are people who care and wish to protect all people.