My quick conclusion is that if we thus assume that male, white, and Democrat are independently distributed, we find that 60% * 80% * 30% = 15% of journalists are white males that identify as Democrats. While this is probably the most common combination of these particular characteristics, it doesn't feel particularly overwhelming.
From what I can tell journalists at major US papers have about a 60:40 male to female ratio: https://www.statista.com/statistics/625800/newspaper-journal.... I also found this interesting source which seem to say that most newsrooms are about 80% white: https://googletrends.github.io/asne/.
My quick conclusion is that if we thus assume that male, white, and Democrat are independently distributed, we find that 60% * 80% * 30% = 15% of journalists are white males that identify as Democrats. While this is probably the most common combination of these particular characteristics, it doesn't feel particularly overwhelming.