Syrian Chemical Attack:

Undoubtedly carried out by Assad's forces with the collusion, and therefore, prior knowledge of the Russians. Nobody was supposed to know about it. Russian drones monitored where the injured were being taken and then that hospital was then subjected to attack in an attempt to destroy all evidence.

Why would they do it? Two reasons as far as Putin and the Assad regime goes:

1: Because they thought that they'd get away with it and that US reaction would be similar to that of the Obama Administration in 2012

2: It would seriously intimidate the rebels and might shorten resistance in the area.

Syrian Chemical Attack - the US response:

The US gave Russia advanced warning of their intended strike, that allowed the Russians and Assad sufficient time to move anything from the declared target area. The strike was a warning and only a warning, it was not meant to "destroy" anything, it was meant to provide a demonstration of what might follow any further use of chemical weapons. In that I believe that President Trump got his message home, but to confirm that we will have to wait and see. Very embarrassing for Russia whose anti-missile Growler system failed to intercept any of the US Tomahawks even although they had prior warning and knew what their target was.

Anti-Semitism Definition:
Exists now in law. Shaw's, Raggy's Gnome's, Greg F's or indeed anyone else's opinions are irrelevant.

As recommended by Chakrabarti - No-one who is a member of the Labour party can be banned from the Party for life for expressing any racist views (Includes anti-Semitism) - doubt that read her report and her conclusions all adopted by Labour's NEC.