Boggs rode of blackguarding Sherbum as loud as he could yell, all down the street and pretty soon back he comes and stops before the store, still keeping it up. Some men crowded around him and tried to get him to shut up, but he wouldn't; they told him it would be one o'clock in about fifteen minutes, and so he MUST go home he must go right away. What is the meaning of the word blackguarding as it is used in this context?

praising loudly

protecting from harm

being verbally abusive

causing a great disturbance