Pat O'Neill, who is favourite to be the Fine Gael candidate in the Carlow-Kilkenny by-election next year caused by the appointment of party TD Phil Hogan as European Commissioner, said the world media was depicting Israel as "the terrorist" but a look at its history shows what Hamas stands for.
Meanwhile, Foreign Affairs Minister Charlie Flanagan defended the Government's stance of not backing an international inquiry into Israel's military action.
But Independent Senator David Norris said Ireland's abstention on the UN vote was "shameful". He said it was better to be one country in the right, rather than siding with all the rest in the wrong.
Mr Norris told the recalled Seanad that Israel was defying the world and "unscrupulously using the Holocaust to justify what they are doing".
Mr Flanagan said the decision to abstain on a UN vote for an inquiry was a collective EU decision. "The cold reality also is that, if a common abstention had not been agreed, there was a very high likelihood of a number of our EU partners voting against the Resolution, thereby reducing overall EU influence even further."
Mr Flanagan said Israel is responding disproportionately to Hamas rocket attacks.
The minister said any use of military force in self-defence must be in accordance with international laws and the level of casualties was unacceptable.
"What we are now witnessing in Gaza is a brutal and utterly futile conflict," he said.
Mr Flanagan said he fears, in particular, for the damage which its continued military operations against innocent civilians is doing to Israel's international reputation.