But then, I don't see much justification for much of Barnabas' actions either. Yeah, he felt bloodlust now and then but there were ways around that without torturing and killing people all around him. As I recall, it was established in the very first storyline that introduced Barnabas that he fed off cattle.
This always did strike me as odd, that in the beginning, after he got released in 1967, he fed on the cattle but later on [spoiler]when we learned he first became a vampire in 1795, became one again in 1897 and during the Leviathan, 1970 PT storyline and 1840 he feeds on humans.[/spoiler] Maybe he just decided human blood tasted than animal blood in the longrun.
Seriously, Barnabas never chose to become a vampire. There were times he honestly did try and resist biting a victim, but the bloodlust was just too great for him. No matter how much he tried to resist, ultimately his bloodlust got the best of him. He did not enjoy being what he was. This to me proves he did have a soul.