Yes, some of my users have asked the option to globally disable smilies. I never knew some people really dislike smilies. An option in the UCP "View smilies", if its unchecked the user can't see the smilie and views just the plain text ( -> : D) ofc without the space.
FWIW, the actual word is not smiles but smilies .
CapnLuffy's suggestion will prevent the graphic from coming up, which very well could accomplish what you want.
I dont think anyone has entirely accomplished removing the smilie dropdown in Xenforo. Xenforo uses the TinyMCE editor, I am sure it is possible to accomplish what you want. It would involve editing the TinyMCE files in Xenforo.