I said the speed of light varies.<quoted text>
It's not wrong.
Incomplete, maybe, but not wrong.
Your statements, that the speed of light varies, are equally incomplete, so by your own admission they are also wrong.
Your statements that the speed of light varies, should read something like, depending on the medium, or when going from one medium to another.
When light is travelling in a single medium, its speed does not vary. It is only "c" in a vacuum, but its speed will be constant for each medium it travels in.
You can admit you were wrong now.
And you want me to admit what?