1) But the discussion is about female protagonists and quite a few men play those characters. And I don't think anyone is chiming in out of spite. People are just expressing their opinion. I'm sorry if you feel like we're attacking you're feelings just to be jerks. I know that's not my motivation. 
2) I'm sorry if I've given the impression that I'm doubting feelings because I'm not. I'm a person that is very empathetic to my character's feelings so I understand others who are as well. But like I've said, I'm just trying to understand why so many people seem to consider Blackwell's actions unforgivable. I agree that bedding a woman and then leaving is an awful thing to do, and I'm not questioning that. My question was why is Blackwall doing it a "tragic romance" when other characters walk out on the PC immediately after sex, but those are NOT considered tragic. For example Fenris has sex with Hawke then leaves him/her for three years because he's so overwhelmed with the feels. But I don't see anyone calling Fenris horrible. Morrigan also leaves immediately after sex with her love interest and on the eve of battle, no less. And she's gone for two years. But her romance is called a happy ending. Why is only Blackwall an unforgivable jerk for leaving the PC alone in bed? I'm not saying he's not, I'm just curious as to why it's worse when he does it.
And to be fair, the Inquisitor seems fine with having sex in a barn with no doors that guards/random NPCs wander into all day long. So her being in a barn where everyone can see is her own doing. Though I really don't get that... you have a bedroom, Inquisitor! Why are you not up there! Who the heck wants to have sex on a haystack??
I'm also curious as to why so many people feel his crime is unforgivable whereas other characters commit crimes as well, but are considered okay. If I'm reading your response correctly, for you it's the fact that he was paid to kill a man that bothers you. What about other folks? Is it the money that bothers everyone? If so, why is Zevran considered a happy ending romance when he's paid to kill lots and lots of people? As was Leliana as a bard. Are they different or is any LI being a paid killer a deal breaker for a lot of people? Personally, Zevran is one of my favorite Dragon Age romances. 
1) It's not that, it's just that I don't understand why people keep bringing up female LIs in this context. I also feel like that this thread was made so people could make their voices heard in hope that a BioWare dev that lurks around will take note of this. It wasn't started with the intent for it to become a discussion thread about LIs, I'm not sure how much the OP expected people to attack them (you aren't attacking anyone, sure, but I've seen people just commenting to ****** us off or to diss us).
2) It's nice of you to apologize, but there was no need to 
It's different because you don't wake up to find out these people disappear, they are still there after the act and they don't leave you naked & vulnerable. It's different because their reasons for doing such things are different. Blackwall's past was something I personally had an issue with. I can sympathize with many many of the characters in the game, a lot of the villains do stupid things out of misjudgment and I feel for them (even Lord Seeker Lucius - when he went on rambling on why he did what he did, I felt bad for him), but when they do it out of pure greed I don't feel anything for them. Blackwall's not even a villain, he's just a sad man with a past & his crimes were committed out of pure greed. I'll forgive Solas quicker than I forgive Blackwall (I already forgave Solas, but that's partially because I'm so uber biased with everything related to that guy). Zevran & Leliana did bother me, but only a little compared to Blackwall, these are their occupations, and their occupations were affected by their upbringings.
I'm not sure why, the concept of being an mercenary/assassin/whatever and getting paid to kill people doesn't bother me as much as a person who accepts money/gift to kill someone, the person who gave him that job wasn't his superior afterall, he could've refused.
TL;DR It's more complicated than that 
And. I have no idea who thought it was a good idea to have sex in a barn O_o.
I can't imagine how lying naked on a haystack wouldn't be itchy as hell.