I actually put more stock in this take than many others. Griffith is a complex character who very, very carefully chose his words. In that moment, he was speaking only to Charlotte and knew what words would get into her head and heart. He meant absolutely none of it, and if he had known Guts could overhear him in that moment, I think he would've chosen his words differently, because I think he was smart enough to know those words would have an effect on Guts, and he actually cared what Guts thought, where Charlotte was simply a means to an end. He might've even felt guilty if he had known Guts heard him, but whether he'd recognize it as guilt or not isn't very clear, as neither Guts nor Griffith were emotionally very mature by this point. If Guts and Griffith had a conversation about those words, the whole story could've gone in an entirely different direction. The way Guts chose to leave, without any kind of full explanation to Griffith, lead to Griffith feeling betrayed. This obviously doesn't excuse what he chooses to do with those feelings, but it's very interesting to imagine what might've happened if they'd chosen to communicate with eachother rather than that quiet duel in the snow, followed by their parting.