Nelson shouldn't be held responsible for the decisions of his political masters. Parker's orders were to frustrate the Armed Neutrality, by force if necessary. Once negotiations broke down Nelson's job was to bring that force into play and finish the fighting with as little bloodshed as possible. If that meant threatening to launch fire ships at them to force a surrender then so be it. If it meant actually carrying out that threat then the responsibilty lies as much with the apparently surrendered ships as it does with Nelson.