Does being bipolar justify emotional abuse? I don't get it

Idk what it is but I seem to attract bipolar guys and my ex was emotionally abusive (all the time) because of it and now the guy I'm hooking up with says he's bipolar but idk, he's usually a great guy (despite being emotionally unavailable) but he will occasionally all of a sudden switch and start being an asshole and I confronted him about it, told him i don't want to deal with him with he's being a dick to me for no reason and his reply was 'I'm bipolar, idk, if I'm in that mood then I'm in that mood, I can't change it'. 
Is that a thing? I know they switch in and out of mood but does that justify being emotionally abusive because they 'can't control it'? How do you deal with bipolar people? 
I feel like I have to walk on eggshells around them just in case I trigger them into being that way.