This film is about a man trying to change things. He is gay, and its a motivator for him, but it is not all that he is about. Instead, this is about power changing in peaceful ways and the violent reaction against it; first in words and attempts at passing laws, and then violence on the part of one man. Most interesting is that it does not try to judge anyone or create a saint, but lets the footage tell a story.
Good things to point out are that not only Milk but the straight mayor were killed, the peaceful reaction to this violence, the violent reaction to the verdict (what happens when system fail to be just), the reaction of the government to the destruction of property (as opposed to two murders), and that Dan White's life ends in tragedy, too (suicide). All around, a positive movement ends in all around tragedy.
The movie "Milk" was based on this, and botches the job in every way. I like Sean Penn, but it was horrible and preachy.
If viewers are homophobic they will not be comfortable with the film, but anyone with some curiosity and tolerance will see it as a struggle of the individual and for rights. This film is not about sex or love, but political power and respect. There is some language, but if you are open to the topic the language will not shock. Overall, it is appropriate.