The claim that critiquing Israeli policy is antisemitic stems from what is usually the unequal treatment Israel's critics devote to Israel. An extreme case in point, is UN resolutions against Israel which amount to almost half of all their resolutions. That's absolutely absurd, when you consider what's going on in countries like North Korea, Syria, etc.
We can also use, as example yourself. You've made multiple threads criticizing Israel's treatment of Palestinians. I haven't seen one thread criticizing eg. Saudi Arabia's treatment of women, alAssad's treatment of his own citizens in Syria, Yemen, or any thread dedicated an Arab country's human rights violations. I didn't find any threads from you about the death camps of North Korea, the Russian war to annex Crimea, Sudan's routine killing of women for adultery or slavery in Pakistan.
Belgium halted funding for PA education after an elementary school there named itself after a terrorist who murdered 13 children. Why did you not make a thread about a PA elementary school that names itself after a murderer of 13 children? Hamas funnels about half of the aid it receives from the EU - not to charity, education, and health, but to building tunnels it can use to capture and kill Israelis. Are you familiar with the living conditions in Gaza? Why did you not make a thread about Hamas ignoring it's civilian's needs?
I can go on and on and on. To be fair, I did find a thread you made about racism in India. I could not find any threads specifically addressing any humanitarian crimes in Arab or African countries. As you've noted in another thread, Muslims have difficulty criticizing Islam. What you have yet to note is the difficulty in criticizing the umma. This follows the famous Arabic line (there are different versions), "I will support my brother against my cousin, I will support my cousin against the stranger".
So that is why criticizing Israel is often perceived as antisemitic.