the subjunctive tense

Timothy Barnard of Montreal complains (LRB 26 Mar 09) about grammar: "The LRB and its authors continue to have problems grasping the use of the subjunctive tense in English. Henry Siegman writes: 'Even so, it offered to extend the truce, but only on the condition that Israel ended is blockage.' Does one have to be of a certain age for this to grate on one's ears? Israel never ended its blockade. Hamas offered to extend the truce on condition that Israel end its blockade, which it refused to do." To which the editor responded: "If Timothy Barnard hadn't called the subjunctive a tense we would have been more ashamed of ourselves."