While Ron may have consistently had a short fuse in canon, there is no reason for him to not have taken a calming potion prior to dealing with the one person he knew he would need one for - Draco Malfoy.
This does broach one concern I have had about the Ministry of Magic. They have an artifact whose purpose is unknown. They only know that whatever gets sent into it never comes out, that they know about. So they use The Veil to "execute" their prisoners. Yes, magicals have little intellect and less sense.
A good, true-to-canon characterization.