I realise there are some on here who make heartfelt and legitimate critiques of corbyn and Labour, but here is one for the daily mail headline shouters (not that anything could get through to the rabid flag wavers)
I don't think many think Corbyn himself is anti-semitic - although it's been worryingly close to being able to seriously level that charge at him. No, the accusation that has reasonably been laid at his door is that his hatred of Israel has allowed anti-semitism to thrive in the party and that he's been unable to separate the two successfully. His attitude has acted as an enabler for those who hate Jews in the rank and file.
When he challenged the IHRA definition of anti-semitism is a case in point - it was totally unnecessary to do it, but he couldn't help himself.
Because Corbyn hasn't led effectively on the issue, that community (not all but a sizeable amount) are now worried it's the tip of the iceberg, and that Corbyn in power would enthuse these anti-semites even further.
Bercow is basically saying exactly that - the problem exists, but Corbyn himself is not an anti-semite.