Oh I got your meaning now I think.
Basically, what you're saying has nothing to do with love or romantic sentiment.
You're saying (if I understand you correctly) that because Lelouch knew how loyal Kallen was to him, and he didn't want anyone else to die due to him, he severed ties with her to keep the Black Knights from killing her.
If that's what Okouchi was trying to convey, he did a really bad job of it IMHO.
I agree with Ami Koshimizu (the VA for Kallen), the kiss between Lelouch and Kallen was unnecessary to convey him ending their friendship.
Ms. Koshimizu stated in Animedia Jan issue of 2009 that she was taken "off guard" when she was told her character was going to kiss Lelouch.
I can see why.

As a side note I thought I should say that I really do like Kallen very much as a character.
However, if the intent of Okouchi was to make Lelouch love her than by God, why the hell didn't he just go ahead and do it.
It's frustrating when we are given all this love between CC, Shirley, Kallen, and Lelouch and then we aren't given an official pairing.
I know that the Japanese do this a lot in their story telling styles, but in Code Geass I think they were just trolling us the whole time.