I like to counter this argument with British Slang is more horrid than so-called "every day American slang".
Seriously, I hate it when I hear a Brit say Telly instead of Television, a Hover instead of a Vacuum Cleaner (Hover is a brand name, like I hate how Americans say Xerox instead of photocopy).
Series instead of season. Last but not least loo for toilet or bathroom, I can accept the term water closet, but Loo? It sounds french and I though the British hate the French.
Look in the 1770's we beat you guys up for liberty and your language (and you are not having it back), it is ours now, deal with it.