Completely agree. I myself have used GUIs for a long time (SourceTree, GitKraken, GitHub Desktop...) and they are very useful for the basic workflow. Unfortunately it is very easy to mess up sometimes with Git, so knowing how it works internally and being able to understand its command line interface will be very helpful.
However Git commands (as a good Linux/Unix command line tool...) are very difficult to understand/memorize. As an example, what does the -d option mean? well, it depends on which command it is applied...
On a daily basis, I would say it's perfectly OK to use GUI clients, especially if they make you more productive! But try to use command line once in a while in order to become more familiar with it, it will help you in the long term.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.