Sora falling for Matt isn't something that is Matt's fault. He can't control who she cares for any more than Tai or Sora herself can. Tai took the high road and allowed Sora to follow her heart when it became clear she was in love with Matt.
Matt DID have control over whether he accepted to feelings. He knew Tai had been in love with Sora for years. He knew this because he was Tai's best friend. He never indicated he had any particular special feelings for Sora either. And despite this, HE STILL FUCKING SWEEPS HER UP.
THAT is why /a/ hates Matt. Saying he stole Sora isn't exactly right, so I just prefer to go with "Matt is a dick."
His crest is FRIENDSHIP for gods sake! What ever happened to Bro's before Ho's?