Arafat is a terrorist, but then Sharon is a war criminal who can't visit Europe without diplomatic immunity or he faces arrest.
In 1982 Sharon was defence minister when he authorised Israeli allies to enter 2 Palestinian refugee camps in Lebanon, Shabr and Shatila. The Israeli's Christian millitia allies were intent on revenge after their prime minister had been asassinated. They massacred 3000 Palestinian women and children in revenge, after being allowed into the camps by the Israeli army, under the orders of Sharon.
It's not an isolated incident either. Look up Dir Yassin, the Palestinian village where the civillians inhabitants were massacred in 1948. That was carried out by the Stern gang and Irgun, led by Yitzhak Shamir an Menachim Begin, both of whom later became prime ministers of Israel.