"Negative" versus "Minus" As a math educator, do you think it is appropriate to insist that students say "negative $0.8$" and 
not "minus $0.8$" to denote $-0.8$?

The so called "textbook answer" regarding this question reads:

A number and its opposite are called additive inverses of each other because their sum is zero, the identity element for addition. Thus, the numeral $-5$ can be read "negative five," "the opposite of five," or "the additive inverse of five."

This question involves two separate, but related issues; the first is discussed at an elementary level here. While the second, and more advanced, issue is discussed here. I also found this concerning use in elementary education.

I recently found an excellent historical/cultural perspective on What's so baffling about negative numbers? written by a Fields medalist.
I am fully comfortable with "minus $x$," and indeed like it better than "negative $x$," and have seldom used the latter in lectures. 

There is no problem with the binary operator and the unary operator having the same name. Speaking and writing mathematics would be more awkward if we did not allow useful abus de langage.
In logic 

the negation of a certain element in a set is all the other terms in the set 

for the set     $\{1,2,3,4\}$

the negation of the element 2 is 

$\neg 2=\{1,3,4\} $