"If it's important to you, he should be here"
A scene that doesn’t seem to get much attention—but one that expertly showcases Charlie’s maturity and sensitivity—takes place at the Sadie Hawkins Dance when Charlie asks Sam where Craig is. She explains that school dances aren’t really Craig’s thing—something along those lines—and Charlie says something like, “If it’s important to you, he should be here.”
If you love someone, you should want to support her, which includes supporting—and being around for—her interests.
A great Charlie-Sam moment, IMO.