There are several ways in which this task could be approached. It would be possible to focus on the economic conditions then and now as a cause for fragmented social relationships: a thesis statement could be -
Unskilled workers encounter the same sort of social alienation, violence and detachment as the characters from Steinbeck’s Of Mice and Men.
Of course you will need to find examples of specific behaviors from everyday life which can reflect incidents from the novel. I suggest looking over news articles and perhaps work related suicides or violence in unskilled workers. The US Department of Labor website may help in framing your understanding of workplace violence and bullying. This could be interesting in the light of Curley’s attitude towards the other men.
Another angle could be to look at the support offered for unskilled laborers when they suffer an industrial injury, as Candy did in the novel. A possible thesis statement could be-
Modern labor laws are still ineffective in supporting unskilled workers who sustain workplace injuries.