In the 1970s, Walter McMillan started his own pulpwood business. He saw that there was a growing trend of poverty and persistent unemployment among African Americans and wanted to escape from that by becoming his own boss.
Walter borrowed money to buy his own power saw, tractor, and pulpwood truck. By the 1980s, he'd grown his business into a thriving concern. Although it didn't make Walter a huge amount of money, his pulpwood business still gave him a lot of independence, certainly a good deal more independence than those forced to work for white business owners.
With independence comes a fair amount of respect. But it also brings with it a fair amount of contempt and suspicion from white folks. They believe that Walter's level of success is way beyond what an African American with a limited education can achieve through legitimate means.
The implication here is that Walter has somehow resorted to criminal and/or underhand means to achieve success in business. The white folks of Monroe County are so bigoted, so steeped in hate, so blinded by racial prejudice, that they simply cannot conceive of an African American starting his own business and working hard to make a success of it.