It depends on your point of view. Although Haig was the overall Commander-in-Chief, the responsibility for planning the offensive lay with the local Commander, Rawlinson, I think. He drew up a plan that involved several weeks of artillery bombardment, the objective being to destroy the German trenches and cut the barbed wire lying in front of them. He issued orders that the first waves were to march slowly across no man's land, carrying 50 lbs of equipment, including shovels which forced them to remain upright. They were assured that the Germans would all be dead and they could simply walk in and occupy their trenches. Contrary to what others have said, there was no creeping barrage. The artillery stopped before zero hour, allowing the Germans to get out of their trenches and set up the machine guns. The artillery had failed to destroy the trenches, or to cut the wire, as many of the shells proved to be duds. The result was carnage, with the Britich Army suffering 60,000 casualties on the first day, almost half of whom were fatalities.
As for blame, the plan was Rawlinson's, but Haig had serious doubts about it but chose not to undermine Rawlinson's authority. My view is that if he did not believe in the plan he should have rejected it.
As to the general charge of butcher, Haig appears to have accepted that the war of attrition would ultimately bring success, and that the casualties were a necessary evil.
In later offensives, creeping barrages were used, with lightly equipped assault troops storming the trenches before the defenders could set up their guns. While there were inevitably some casualties from friendly fire, they were few in comparison with what had gone before.