>>715338863
>No, seriously, how the fuck do you counter this?

Defensively.

Use caltrops or just dig a bunch of holes on the battlefield and let the horses break their legs then slaughter the riders after they fall off. Phalanx style shield wall tactics could help your infantry weather a barrage while your own archers fire back.

If they fight you on an open plain without any defenses built into it then you're pretty screwed although having your infantry carry caltrops that could be deployed as an improvised fortification would help; but you'd need to have a field of caltrops deep enough that they couldn't fire accurately