It's not clear in the rulebook about discards.
When a player is forced to discard any number of cards - is it their choice, random or the other player's choice? This has come up in a few games I have played so far.
The player who discards chooses which card to discard.
It wouldn't be so if the rule stated the the player discarded cards at random, or that the active player could look through the opponent's hand and choose for them cards to discard. But worded the way it is, the player chooses.