I've worked with numerous UI designers/frontend devs who have never used the command line (purely because they've never needed to). The learning curve of git is steep enough without having to teach them the command line.
The only situation in which I could claim to agree with this is if there is a super hard core and time intensive task where there is no room for learning at all, and all that matters is that a product gets out as fast as humanly possible. If that's your situation and you can't handle command line, so be it go for a GUI. But if your free time I still think you should be practicing command line.
People /should/ know how to use the command line, even if they prefer to use other tools daily, but often it's not practical to force people to use it.