I'm not saying the Robot and Monster will hurt Kizaru because they're made out of light, I'm saying they CAN hurt Kizaru because they're made out of light.
IE, the Robot and Monster holograms can punch Kizaru when he's using his powers, because he's also made of light at that point.
Like, when Kizaru isn't using his powers, he's physical matter, and the Robot and Monster are video game characters, holograms.
BUT once Kizaru is using his powers, he's also a being made of light, like the Robot and Monster, so I think they'd be able to physically interact with him, IE fight him.