So when Victor Hugo says that Grantaire loved Enjolras, why does it automatically mean that Grantaire wanted to have sexual relations with Enjolras?
There are so many different types of love that are expressed in Les Miserables, including unrequited love for another human being (Eponine). The way Grantaire loves Enjolras is the way that people love whatever god they believe in. Grantaire "venerates" Enjoras; Grantaire does not lust after Enjolras.
The Death Sequence
I see more religious imagery than I do romantic imagery. Grantaire is a sinner, he has repeatedly let Enjolras down. Grantaire is now standing on the threshold to heaven, and he asks Enjolras, "Will you permit it?" Will you permit me to enter paradise with you? Is my sacrifice enough to please you? Enjolras lui serra la main en souriant. "Enjolras shook [Grantaire's] hand and smiled." A handshake of welcome. Welcome to the afterlife, my disciple, my faithful friend. You are welcome to come and die with me.
They die as they shake hands; they do not die as they hold hands.
To compound the religious imagery, "Grantaire, struck down, collapsed at [Enjolras'] feet." Here is a man literally at the feet of the man he worships. Different people sit at Jesus' feet during different points in the Gospels, and the fact that Grantaire dies in such a position is highly religiously symbolic.
Orestes and Pylades
Victor Hugo choose to describe the relationship of Grantaire and Enjolras as similar to the one between Orestes and Pylades. "Oooooh!" fanfiction writers exclaim. "Orestes and Pylades were Greek homosexual lovers--obviously that means Grantaire and Enjolras were too!"
In all the stories about Orestes and Pylades, absolutely none talk about Orestes and Pylades being anything more than friends that were so close they considered each other brothers (they were actually cousins raised together). The only mention of anything but a platonic relationship comes from Lucian's Amores, a writing in which two men--one heterosexual and one homosexual--argue about which form of love is better. The homosexual man says that the close friendship, the willingness to lay down their lives for the other is an argument for homosexuality. (The implication is that because men and women can't be friends, they can't be lovers as well as men can.)
However, I don't think that friendship equates to sexual attraction either. Everything else written about them only talks about their friendship.
What do Orestes and Pylades say about Enjolras and Grantaire? That Enjolras doesn't completely disdain the poor drunken Grantaire. There is a connection there. Enjolras wants for Grantaire to better himself. This idea is expressed further when Enjolras gives Grantaire the chance to go to one of the sections of Paris to stir up the ideas of revolution.
No.
Victor Hugo labored over a decade on Les Miserables. Now, anyone with the internet can take his carefully crafted characters and make them do whatever they choose. Enjolras is a perfect character exactly because he is this virginal Apollo that believes only in freedom and equality. Grantaire is a perfect character exactly because he is this ugly alcoholic student that believes only in the believer Enjolras. The lack of sexual relationships is such a crucial part of Les Miserables. Look at Jean Valjean, at Javert, at Eponine, at the whole host of nuns and priests and unmarried sisters that make appearances in the novel.
If you want, write about the questionable relationship between Laisgle and Joly (including their grisette Musichetta) because there may have been something there. However, don't ever mistake the veneration that Grantaire had for Enjolras as desire to get into Enjolras' pants.
So please, please, please, if you have any respect for Victor Hugo and Les Miserables stop the E/R fanfiction.