Sirius' "joke" on Snape

[atelecky at mit.edu]

No: HPFGUIDX 6182

In PoA, Lupin describes how Sirius thought it would be "funny" to 
tell Snape how to get past the Whomping Willow, so that Snape 
would find himself confronting a full-grown werewolf if he tried 
to spy on the "Marauders" again. Does the idea that Sirius played a 
"joke" on Snape that would almost certainly have led to his death if 
James had not intervened really disturb anyone else with regards to 
Sirius' character? Might there have been some better reason than 
Sirius' simple dislike for Snape, some specifc event, that would have 
led Sirius to go that far? We have not, after all, been given many 
specifics of the relationship between Snape and the Marauders; other 
than the fact that Sirius considered him a slimy little worm, we are 
given no real reason (though there is really no reason good enough) 
for Sirius to have wanted to actually put Snape's life in serious 
danger.

Any ideas? 
Alexandra