Noah's anger was not directed at the monsters who tried to kill him, but at his "teammates", the other warriors who had not gotten the monsters' attention... The way they were acting was infuriating him.
Noah was used to breaking into Fortresses with the members of the elite team he had previously, or breaking into them alone like that time using only the imps, so he knew what each one was supposed to do and how a poorly executed action could cause a problem for the whole group.
Seeing these people attacking in such an unbridled way made Noah angry, as the warriors were fumbling while the archers and wizards just shot arrows and spells without caring about anything. If it weren't for Noah being so flashy, these wild boars probably would have already been angry with the magicians and turned to attack them.