It appears Realized Gains (or Losses) cannot be selectively deleted as a Category in the production of Income/Expense Reports/Graphs customization. Investors do not always consider capital gains or losses when selling an asset as either income or expense in the same way as other income and expenses.
An investor who sells Asset A for X proceeds (and some Realized Gain or Losses) may right away invest those funds into new Asset B. Neither of those activities are true income or expense in the classical sense. We should be able to 'uncheck' a box that eliminates those transactions from Income/Expense reports.