I've never kept blackthroats, but I do know that with the species I keep (V varius) there are no hard and fast rules as to what happens when males are kept together and you may find it is the same with blackthroats.
For either species, most people would tell you that two males will definitely not get along, that they'll fight for dominance eventually ending in the death of one of them. The only times I've introduced adult male V varius outside of their enclosures, they wrestled for dominance, but my breeding pair (which get along 24/7 inside their enclosure) also react in a similar way when introduced outside of that enclosure - the male puts on a dominance display and chases the female around. Very inconclusive. I also know of many people keeping groups of V varius in mixed lots of males and females without problems. One local fauna park swears that the best way to display them is to house several males together and they'll get along provided there are no females, while other people I know have two or three males together in enclosures with three or more females.
There are, of course, also plenty of stories of males fighting and doing tremendous amounts of damage.
And there are cases of opposite gender 'pairs' of monitors in which the males have killed the female, and vice versa.
So, in the end, no one here can guarantee that they'll fight or that they'll get along. Your chances of them getting along might improve, however, if you traded one of the males for a female.