The answer to this question can be found by analysing Chapter Seven of Book the Second, in which this event occurs. Dickens goes to great lengths to emphasise the cruelty and the lack of compassion of the Marquis in this episode, and the way he responds to the news that his carriage has killed a peasant child only serves to reinforce our earlier impressions of his character. As he is confronted by the father of the child and the faces of the crowd, the Marquis is said to look at them "as if they had been mere rats come out of their holes." Then note what he actually says to them:
"It is extraordinary to me," said he, "that you people cannot take care of yourselves and your cihldren. One or the other of you is forever in the way. How do I know what injury you have done my horses? See! Give him that."
Note the contempt with which the Marquis responds, and the way that he considers his horses to be more important than the life of another being. The equally contemptuous gesture of tossing a gold coin in recompense for the life that he has just taken again shows his extreme arrogance and his view of the French peasantry as being little more than objects to be bought or paid off.