Their policy is also stated in their charter, which goes beyond just killing all Israeli civilians. It says they will kill all the Jews everywhere in the world.
But perhaps you'd prefer to see actions - Israel is currently engaged in urban combat with an enemy who intentionally uses civilian infrastructure (a war crime, by the way). There will be collateral damage from this, especially when Hamas don't allow civilians to evacuate out of the heavy combat areas.
Hamas on the other hand are continuing to launch rockets daily at civilian targets in Israel, intentionally targeting civilians while celebrating every rocket siren.
Jabalia Refugee Camp was established in 1948.
It's not a temporary housing measure. The buildings are all high-density multi-family dwellings constructed from reinforced concrete.
Calling it a refugee camp cheapens the word for people who are displaced from their homes and forced into temporary housing during a war.