"What is being implied here?"
In the statement that included the ethnic differences, as RFK attempted to explain in his testimony, the published research he was discussing involved differences in ACE2 receptors in the different ethnic groups, and that is the mechanism by which the spike protein on the SARS2 virus 'unlocks' the cell surface and gains entry into the cells where it can co-opt the DNA machinery and pump out new viruses.
There was no implication in his statement. He was simply discussing the published research that detailed the variable effect of the SARS2 virus on different ethnicities and why that was seen, which was because of the difference in ACE2 receptors the different ethnicities have because of the genetic difference of their DNA.
His words were taken out of context, and the Senator questioning him deliberately prevented him from adding that context, which you can see happening when you watch the interlocution between them.