I think it's really important to mention that mental illness doesn't make a person antisemitic or make them say all the horrible comments he's made. We shouldn't excuse it just because he's also mentally ill. Solely blaming his bipolar disorder only serves to stigmatise others who are bipolar. Many people with mental illness, especially bipolar, are horrified by his comments and have come out to say that antisemitism is not a symptom of bipolar disorder. Most with bipolar would never say these things unless they also believed it.
I do think his mental health is impacting his actions and his inhibitions when it comes to saying this stuff openly. I don't think his mental illness is making him an antisemite.