I did:

• Search for if my issue has already been submitted
• Make sure I'm reporting something precise that needs to be fixed
• Give my issue a descriptive and concise title
• Create a minimal working example on JsFiddle or Codepen
  (or gave a link to a demo on the Selectize docs)

Steps to reproduce:
JS fiddle

Expected result:
image

Actual result:
image

because remove_button plugin assumes item class on the outer element of the item, but if you provided a custom render option and didn't provide item class, you will get broken css