
Heterosexism aside, in the Harry Pottermovies, Rupert Grint was well aware of the homoerotic undertones in the original novel between his character, Ron Weasley, and teen wizard Harry Potter. So in the movie series, he imbued his character with a tenderness, a vulnerability, and an eye-bulging desire that was not mitigated by the scripted romance with Hermione.
And after Harry Potter, he has chosen a number of buddy-bonding projects (as well as projects that allow him to display his respectably buffed physique and Burt Ward-sized package). Cherrybomb (2009), for instance, involves a sex-and-crime triangulation between Rupert's Malachy and Robert Sheehan's Luke.
In Wild Target (2009), a middle-aged hitman (Bill Nighy) takes on a young apprentice (Rupert) and a hostage (Emily Blunt), and proceeds to fall in love with both.
In Into the White (2012), Rupert plays a British pilot shot down over Norway during World War II. In order to survive, he must share an isolated mountain cabin with a German pilot. I haven't seen it, but it sounds like it's tailor-made for homoerotic buddy-bonding.
Rupert has not addressed the usual gay rumors, but there is no doubt that, like his Harry Potter costar Daniel Radcliffe, he is a gay ally.