Back in 2003(i think) an act got passed that gave young Brazilians a minimal computer and internet access for free.
Ironically, around the same time, Ragnarok Online's server code was leaked, and private servers began to pop up all over the place and became wildly popular on the internet for a free and fun online game.(Especially since you could max your level in a few hours instead of years)
These young Brazilians fell in love with Ragnarok Private Servers due to it's free access and ease of running on computers and would flock to servers. However, many of the servers that used their regional code were primarily English.
The admin's of the servers began to make laws that you can only speak english when in the normal chat, and you must use Whispers or Private messaging for other languages. These rules were widely ignored. Players got tired of approaching someone and speaking to them to only be replied to in Portuguese. Many people petitioned for Portuguese RO servers they could go play on, but the English servers were usually far more maintained and had higher populations, so the Brazilians remained on the English speaking servers.
Well, it became more and more noticeable that players playing on the servers were not speaking any english at all. Quite a few admins of these private servers became distressed as English speaking players began to leave for servers with more strict rules about language.
Then in early 2004, many of the private admins began posting a rule that you may only speak english on their servers, and if you spoke out in another language you would be banned.
Needless to say, many of these new wave Brazilians were banned on the spot. A huge uproar in the Brazilian community occurred. In a certain Brazilian forum which is now dismantled after all these years, they would organize raids and clans to fight English Speakers on english servers.
Some joined out of spite, others joined because it sounded fun.
Huge groups would reach max level and travel in packs on PVP servers and ask "BR?"(One place where the BR phrase became popular)
If you failed to reply in Portuguese, they would camp you, sometimes for hours speaking poorly worded english insults suggesting you log off.
This led to an intense hate of Brazilians on these RO servers. Huge clans would form anti-BR Brigades and hunt down Brazilians. It became a literal online race war.
Well, slowly, the RO Private server fad died. However there were still plenty of bitter players who took their hatred to other games. Even though many of these Brazilians had nothing to do with that hard core trolling of English servers, they were attacked for being Brazilian or having BR in their name.
Warsong on the World of Warcraft server became widely known as BRsong after it became an unoffical Brazilian server. Which spawned hate by the english players remaining. That took it's course through the whole of WoW's already nasty community.
Similar events have occurred throughout all of MMO-gaming leading to this severe hatred of a certain gaming population.