You really cant argue with them if thats their policy. Check out http://www.dslreports.com/ they cover al sorts of providers, cable too.
If they are in fact throttleing you, it is becasue of the P2P type connection. Try using a torrent application and see if it trottles back with that, so you can see if you are in fact being throttles. You may beable to have them stop if you let them know it is becasue of a game and not illegal torrents.
Keep in mind that just becasue your connection is fast does not mean who/what you are connecitng to is.
In all likelyhood, the only solution is to let them know by leaving them and goind with a different provider.