Maybe we disagree as to the facts. A definition of 'massacre' is:

"A massacre is a specific incident which involves the violent killing of many people[citation needed] – and the perpetrating party is perceived as in total control of force while the victimized party is perceived as helpless or innocent."

I think the Israelis regard their actions as responsive and defensive in respect to the fact that their population is under general attack.

I think some people are being perceived as antisemitic because they are taking an attitude that Israel's very success in defending themselves has resulted in lopsided casualty counts, therefore 'it isn't fair', and extrapolating this to justify attacks on Jews in Europe.

It reminds me of the child's complaint: "Dad, Johnny hit me back!"