When reading Bernard Shaw's Arms and the Man, one might respond negatively to Sergius. He does, after all, attempt to cheat on his fiancee, he's demeaning and domineering (even to the point of violence) to the servant Louka, and he comes of as a hypocrite.
But I sort of like Sergius. Rather than calling him hypocritical, I see him as conflicted over ideals like "Honor," "Nobility," and "Heroism," under great pressure to maintain an image that he doesn't quite believe in. But more than that, I just think he's funny. He's a cad, but an amusing, harmless sort of cad. His seduction of Louka is hilarious--he attempts to kiss and grope his fiancee's maid, and when she responds by speaking disrespectfully to him and about Raina, he lectures her about the honorable behavior of a "gentleman" and the proper behavior of a maid. Louka's response is classic:
"It's so hard to know what a gentleman considers right. I thought from your trying to kiss me that you had given up being so particular."
It's not that I necessarily find Sergius sympathetic (though it is possible to do so--he is wrestling with the same doubts about stated ideals as Raina). It's just that I find him amusing, not the least bit detestable. If I read the play hating Sergius, I might not be able to laugh at him.