If someone wants to protest Harris they were never going to vote for her in the first place. This is for people that have done no research and are wavering. Stein shouldn’t be seen as an option (for a multitude of reasons) and for this select group of (potential, and likely minimally politically active) voters this will be the only exposure to stein they will be getting.
If someone was considering stein before seeing this the worst that will happen is they will end up voting for her which was already likely, the best that will happen is they change their mind.