To be honest I didn't notice the link.
I agree that Hamas and Hesbollah are reactionaries.
Whether or not Corbyn, as a lone MP -- in an era where genuine left-wing Labour MPs are hard to find -- could do exactly as you (we) want him to do is an open question.
Would denouncing H & H as reactionaries help the cause of diplomacy/negotiations with Israel?
I wish there was an organized Palestinian working-class Left for Corbyn to relate to in the occupied territories. I don't know of one. The best group I can think of is the Palestinian National Initiative, which only exists (as far as I know) in the West Bank, and has no innately socialist content to it.
It would've been better for Corbyn to describe H & H as dedicated to "social welfare" rather than "social justice." They do provide welfare services which remind me, at least, of what the Black Panther Party did in cities in the U.S. in the late 1960s, though of course the politics are quite different (and worse).