The excuse I've heard is that a lot of South American players come from rough neighbourhoods, so getting an advantage by any means possible is seen as admirable. Seems like a pretty poor excuse, since many footballers all over the world come from tough backgrounds.
I think a lot of other South Americans hate Argentina because they are considered arrogant and consider themselves 'better' than other countries in the region because they are 'more European'. I was chatting with a colleague from Chile the other day and he was very much 'anyone but Argentina'.