Over the last year or so Jackie Walker has campaigned to present Labour politics as a drama centred on the alleged "lynching" of herself.
In May 2016 she was suspended from the Labour Party for allegedly antisemitic comments on Facebook. She was reinstated, and then suspended again in October 2016 for new comments (in public) found to be prejudicial by Jewish Labour members. Despite talk about the issue being "free speech on Israel", none of those comments were about Israel, still less were any of them statements of support for Palestinian rights.
Just specifically on Ken Loach, if you watch the interview referred to you will see that he was ambushed with the (as it turned out false) accusation that there had been holocaust denial at a meeting he hadn't attended and he essentially declined to comment: https://www.youtube.com/watch?v=SLXgOCIb0XQ
"Perdition" meanwhile, was inspired specifically by the Kasztner case. Kasztner was actually assassinated by right wing Zionists in 1957 on the grounds that he had collaborated with the Nazis in Hungary by sending some Jews to the camps even while enabling others to escape to Palestine. I haven't seen or read the play and I'm fairly sure neither have most of the people commenting on it. Ken Loach's son-in-law Elliot Levey, who is Jewish, put on a production in 1999 and says it's pro-Jewish. Taking it as read that it's "anti-Semitic" therefore seems an assumption too far.
I know nothing of Erich Fried or of the RAF's line on the holocaust; I wonder if there's cherrypicking and distortion going on there too? While it certainly is valuable to identify and call out anti-Semitism on the left, which demonstrably does exist, AWL's choice of targets, and ungenerous interpretation of others' arguments, often strikes me as sectarian and unhelpful.