Don't start what your not prepared to finish then, there is no need to go calling people naive and belittling them just because they are curious about something they have never heard about. Thats what annoys people and starts arguements, just give them a source if you are so sure that it is fact then we will all believe you.
Thats the first I have ever heard of Dante triggering because of blood, it is never touched upon in the game. My THOERY on it was just that DMC4 was designed as a game for newcomers to the series and the only cause of the triggering was to show newcomers just the arm so they know that Dante is part demon but they are exited to find out what he really is. To me it never really went any deeper than that, but I agree it probably wasn't because he was helpless or in pain.