Tassel Loafers

I know it is traditionally a casual shoe. Is it acceptable in a professional setting?

Um, I think it's the wrong category of questions on sports shoes ...
But it depends on where you work, what material the loafer is done, what you wear, and whether or not it is casual Friday.
I think today it would be nice to wear moccasins in most professional circles as long as you're not wearing a costume. Perhaps with a khaki button-down shirt, sports jacket or sweater, but not a full suit.
Personally, I do not like slackers. Unless they are the kind you can keep a penny in. It's just cool.

idiot you put it in the wrong category!