Railroads being unfair to farmers was an accusation made by the Midwestern Grangers during the 1860s-1880s. The Grangers said that railroad shipping rates were too high. A response to that might be to say that railroad rates are cheaper for farmers than shipping by wagon as farmers did before railroads and as they could do again if railroad rates were higher than wagon rates. That is the polite answer. If you don't mind being callous, you can point out that the nation just fought a big war to establish the hedgemony of the industrial social system and therefore farmers can expect to be used in whatever ways best serve that new system.
Assuming that the farmers are upset over the use of things like eminent domain to take their land or to buy it at depressed prices, I would focus on the positive aspects of the railroad:
-decreased costs for shipping in freight or seed necessary for the farmer
-increased access to markets that would lead to higher profits using the railroad to transport freight
-ease of travel for the farmer and his family, increased local and regional mobility
-access to newer technological developments and tools produced farther away
-decreased prices on equipment thanks to greater access to mail order stores in larger cities, etc.
It would really depend to a certain extent on the nature of the farmer's complaint, whether this is a modern situation or one at the time of the beginning of the railroads, etc.