I can see why you are be so frustrated with debating Muslims... I think it may that you are debating people who really don't know their Deen as you or they may think.
Not for nothing, but this is the go to excuse of Muslims anytime any Muslim is caught out saying something stupid, or saying something violent in front of the non-Muslims, or is otherwise puzzled by challenges or questions put to him or her by non-Muslims. How many times have we, the former Muslims, heard someone explain away bin Ladin, Hamas, progressivist Islam, violence against women, Salafism, Sufism, Shiism, clitoridectomy, Saudi Arabia, women who don't wear hijab, and the rest of it with 'they don't really know their deen?'
It would appear that almost no Muslim really knows the deen.
Which would explain their frustration with your arguments.. they simply don't have the answer, yet still feel the need to defend their faith.
You know, this is a mark of immaturity. If Islam was everything that Muslims claim it is, then they would know that they are unable to defend it, as it stands on its own as the totally true and final and perfected religion of Big Al. Islam says god is all powerful, all knowing, all wise, etc. In such a case, do not Muslims realise what spiritual crime they commit when they presume to protect the one they say created them? If Big Al is everything they say he is, then he doesn't need defending. He could deal with those who criticise or question Islam on his own.
What is interesting to me is that Muslims will do this with each other. Be a Muslim who raises questions about Aisha or about the slaughter of bani Qurayza, and see how your own friends and family will turn against you, 'defending the deen', and telling you to shut up and blindly believe. Just for asking questions or daring to admit that there are things in the life of Mo that make you uncomfortable. 'Defending the deen' is, in my experiences, code for 'shut up and believe... or else, because you might cause me to think!'
always try to avoid things that are offensive, phrasing questions, and arguments in offensive ways.
Seeing as how our mere existence as former Muslims is offensive to many Muslims, I doubt we can avoid that. Muslims claim to be horribly offended by everything - you can't avoid it. It's part of the martyr complex.