i would ask that person (friend) why or what is it about that
particular faith (e.g Christianity) that he is attracted to and why
he wanted to leave Islam.
I have encountered many reactions before, from silence to
understanding to havoc.
Some can be just understanding but some would suddenly get worked
up and start to shoot words that can be hurtful.
What are the views generally among muslims on this??
Do you just keep quiet or go all out to bring the malay guy
down??
I have received emails before telling malay muslims to be careful
of this particular malay christian whom is going around
preaching.
I mean, I find it quite adsurd to be going around making a big hoo
haa over the conversion. 
Yes i would think that the general reaction of most would be
like what u've stated, but it is more important to have a rational
discussion.