Reka You are clearly from the USA (you say "WE certainly went after revenge for that (9/11)
Keir Starmer speaks for the UK. If it had been peaceful Muslims being attacked outside their mosque, he would have spoken of protecting them - ALL the inhabitants of the country deserve to be protected from random acts of violence. That is civilisation.
Any attack calls for punishment of the perpetrator and protection of those attacked, but NOT for revenge. After the October attacks, Netanyahu's reaction has been more than punishment of the terrorists, it has been genocide against all Palestinians. The Old Testament doctrine of "an eye for an eye and a tooth for a tooth", carried out to these extremes, results only in the relatives of those killed for revenge embarking themselves on a campaign of killing multiple numbers in retaliation, snowballing until the whole world becomes blind and toothless.
There is the beginning of an end to the carnage between Isreal and Hamas. It still needs negotiation and compromise, but it could bring peace at last and a chance to rebuild trust and neighbourliness. Speaking approvingly of revenge is inappropriate and inflammatory.