The Emperor of Mankind
Currently the galaxy's spookiest paraplegic
If I see an Islamist group and think that it'll do the same, then I condemn it in similar terms. If there are Islamist groups which are willing to compromise on criminalising homosexuality then they're worth talking about for the sake of ending a war. In other circumstances, they wouldn't be worth talking to, by dint of being Islamists.
The problem with your premise is that it rests on a very flimsy basis. If Islamists are willing to tolerate homosexuality, and if they're willing enough to go against Islamic orthodoxy to do it... that's a mighty big pair of 'if's.
If Islamists are determined enough to enact Sharia law then they'll be determined enough to enforce it - including the parts where it says homosexuality is a sin. How many interpretations of Sharia law have ever tolerated homosexuality? Or for that matter how many countries or groups espousing Sharia law have ever tolerated homosexuality?