I have a problem with this. Every dictionary you look スライダー up in will give you slider.
Every single one.
http://tangorin.com/general/%E3%82%B...83%80%E3%83%BC
http://en.wiktionary.org/wiki/%E3%82...83%80%E3%83%BC
http://ja.wikipedia.org/wiki/%E3%82%...83%E7%A8%AE%29
The last one is Japanese so I highly doubt it's just the Americans getting it wrong. In fact, the Japanese article in particular talks about a baseball pitch called the slider.
スライド (suraido) is slide. スライダー (suraidā) is slider.
EDIT: Oh, they wrote SLIDER themselves? I don't even know why this is a topic of conversation
