2 And, all enraged, thus him loudly shent:
shent > reviled
3 "Disleal knight, whose coward courage chose
Disleal > Disloyal, perfidious (Italian disleale: WU) courage > spirit
4 To wreak itself on beast all innocent,
wreak > give expression to
5 And shunned the mark at which it should be meant,
meant > intended
6 Thereby your arms seem strong, but manhood frail;
frail > weak; morally weak