As the men were not used to the extremely hot climate, they misinterpreted the women's lack of clothing for vulgarity.
Similarly, black men were stereotyped for having a specific lust for white women. This created tension, implying that white men were having sex with black women because they were more lustful, and in turn black men would lust after white women in the same way.
There are a few potential reasons as to why such strong ideas on interracial sex developed. The Reconstruction Era following the Civil War started to disassemble traditional aspects of Southern society. The Southerners who were used to being dominant were now no longer legally allowed to run their farms using slavery. Many whites struggled with this reformation and attempted to find loopholes to continue the exploitation of black labor. Additionally, the white Democrats were not pleased with the outcome and felt a sense of inadequacy among white men.