I guess it's a subtle hint that Greed and Greedling both really want friends. For a guy who claims to want everything this world is offering, he can't seriously think that the crew he has represents a serious threat to anybody, even though all the chimeras are pretty tough.
Also, these chimeras are people who probably felt rejected by the rest of society, whether you take the 2003 or Brotherhood versions. So, it was easier for Greed to approach them and win their trust.
Just my two cents.