In dominator thinking, linking is hierarchical - I'm better than you, more powerful than you, richer, have a better religion, live in a better house, behave better, associate with better people. In a dominator environment, success depends on finding and exploiting differences. And sexual preference is certainly an area where there are differences. By pinning a label on a class of people, dominator thinkers can create a category to which they don't belong.
I am not speaking only of heterosexuals. We are all currently swimming in dominator-tainted waters, and it affects all of us, in some ways we don't yet comprehend. It is my hope that in the near partnership future, the need for sexual preference categorization will be relegated to history of sociology courses.