You’re right, Israel should not get a free pass for genocide or ethnic cleansing.
Hamas began twenty years into the occupation during the first Intifada, with the goal of ending the occupation. Collective punishment has been a deliberate Israeli tactic for decades with the Dahiya doctrine. Violence such as suicide bombings and rockets escalated in response to Israeli enforcement of the occupation and apartheid.
The 1988 Charter, which is certainly unreasonable in its fundamentalism with Sharia Law and is antisemitic, does not call for the extermination of all Jewish People. Hamas wants an end to Israel as an Apartheid State, not an extermination of all Israelis. Under Ahmed Yassin in the 1990’s, truces were offered in exchange for Israeli to withdrawal from Gaza and the West Bank to the 1967 borders. The 2017 Revised charter explicitly accepts a Two-State Solution of the 1967 Borders. Check Article 7 and 13 of the 1988 Charter to see yourself, compare it to Article 20 and 24-26 in the revised charter.