He could have received Israeli citizenship later in his adult years after conscription.
He may have served but in a role that isn’t committing human rights abuses (say working on missle defense)
He may have served but his political views have since developed and he’s now pro-peace / anti-apartheid.
To generalize and assume that nearly all Israeli men are war criminals is to generalize on the basis of national origin which in most jurisdictions is rightfully assumed to be racist.