Unresponsive supervisor blocks submission to conference
Can I remove him as a co-author from the article, even though he supervised the bachelor's thesis?


Based on the information that his sole contributions were to approve the plan and to proofread the thesis, yes, you can remove him as an author.

As a common guideline applied in many disciplines, the Vancouver protocol of the ICMJE specifies the following four criteria for authorship: 


  The ICMJE recommends that authorship be based on the following 4 criteria:
  
  
  Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND
  Drafting the work or revising it critically for important intellectual  content; AND
  Final approval of the version to be published; AND
  Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.