Be careful with your logic and framing. I explained why it was poor framing above. But the way you've (and the gp) framed it is dangerous. Swap "voip numbers" for "x skin color" and you're in clear unethical and illegal territory. But swap the attributes of the parent and you don't get this issue. If parent is x race and all their friends are also x race you're not discriminating against y race through their means because they aren't turning down based on race, it is just closer to changing the odds. The problem isn't when you change the odds (unless there's an extreme manipulation) but rather how you respond to samples from the distribution.
This is wrong. You are expected to discriminate against samples from the distribution in a variety of ways, like the formatting of their resume and their work history; it only becomes unethical when you discriminate based on race, gender, etc. If you replace "voip numbers" with "x skin color", of course that would be unethical, but being able to switch phrases to make them unethical is irrelevant, because we're not discussing the unethical case.
The example of networking you give has even more potential for unethical behavior than filtering voip numbers.
