You've essentially sent an alert to someone ( or a group of people ) saying that you believe their work has no value. This kind of behavior could have real-world consequences. You could be pushing someone to not work on open-source again, or make them feel worse about working on a project they might be required to contribute to as part of their job.
How would you feel if someone started vandalizing your own github projects gvx? Would it make you feel good? Would you consider it funny?