In this case, there is clear mens rea and actus rea. The accused openly stated that he intended to cause a seizure with the hope of causing actual bodily harm. He knowingly used a GIF as a weapon.

That's vastly different from, say, a heavy metal band inadvertently causing a seizure with their stage lights, or an animator inadvertently drawing a sequence that triggers photosensitive epilepsy.

By analogy, consider someone who deliberately drives their car at a bus stop and later brags on social media about trying to mow down pedestrians, versus someone who slips on black ice and spins out of control.

I am fundamentally opposed to "throwing the book" at anyone - I'd much prefer a programme of evidence-based rehabilitation.