It is perfectly possible, reasonable and (I would say) almost certainly true - that you can believe there is a 'small number' of anti-Semitism cases in Labour and that these are abhorrent and must be vigorously and firmly dealt with. This has definitely improved since Jennie Formby took over as general secretary. Ian McNichol and his staff including Sam Matthews (who features in the Panorama programme) were not doing a good job hence the huge backlog.
However alongside this you also have some of the Progress/Labour First anti-Corbyn right wing critics (Watson, Hodge and Streeting are definitely in this category) who have tried to amplify the occurrences and scale of the problem to create mischief and division for their own endless anti-Corbyn agendas. These 2 positions are not contradictory - and can be held at the same time.
As regards the Panorama programme, I think the Jewish Dissident sums it up well:
Ten Facts About The Panorama Documentary
The bulk of the program's testimony was provided by disgruntled ex-employees of the Party, bureaucrats who were unable or unwilling to work with the new leadership, including Iain (now Lord) McNichol. Their claims were accepted uncritically by the interviewer.
Sound bytes delivered straight to camera by anonymous individuals peppered the program. They consisted of unsubstantiated allegations, were low on facts and high on emotional content (much 'tearing up' by the interviewees), and relied on appeals to emotion rather than verifiable data. Their allegations, in some cases verging on the absurd, were not investigated but, again, taken at face value.
So-called 'expert testimony' was provided by authors sympathetic to the paradigm of the New Antisemitism, which deliberately conflates antisemitism with anti-Zionism. These included Dave Rich (The Left's Jewish Problem) and Alan Johnson (Contemporary Left Anti-Semitism). Their motivations and assumptions went unchallenged, and no alternative perspective was put forward.
There was no input whatsoever from the thousands of Jewish Party members who support Jeremy, whose inclusion might have signaled at least some interest in journalistic balance, but would of course have risked damaging the program's pure propaganda value.
There was much recycling of old material - e.g. the Mear One mural and the Ken Livingstone fiasco - in the absence of any substantial new allegations.
There were several telling elisions, like the program's failure to mention that Jackie Walker - whose case was dealt with in a predictably appalling fashion by Ware - is herself Jewish. The Chakrabarti report was dismissed in a couple of brief asides.
Individuals like MP Louise Ellman were able to tell their apparently plausible stories without their own political affiliations being flagged up. Ellman has for many years been a key member of Labour Friends Of Israel.
A handful of leaked emails were made much of by John Ware, but in no case did these emails provide any evidence whatsoever of actual Labour Party antisemitism.
The program's underlying assumptions were that anti-Zionism equals antisemitism, and that Marxists have no place in the Labour Party. These assumptions determined both the tone and the content of the piece.
At no stage were any of the serious allegations of concrete antisemitism alleged by the anonymous participants, or indeed by anyone else, investigated by the program. This made a mockery of its claim to be a serious investigation and clearly revealed it for what it was - an ideologically motivated hatchet job with no concern for the truth.