Is it acceptable to require a student to use the supervisor's preferred software/tools?
Clearly define what are your goals and constraints, and work from there. What are the things that they need to learn in order to progress further in the field (and someday find a job)? What are constraints imposed by the research project you will be working on?


Goals — if learning a specific piece of software is required to become a professional in your field, then it is a de facto standard and they need to learn it. In this, a specific piece of software is just like a particular experimental or mathematical technique.
Constraints — there are cases where you need to restrict the choice of software to interoperate with others. For example, the student might not be able to choose his favorite programming language for a specific project because he has to use a specific advanced library, which only exists in e.g. Python. Or the project actually is to implement a specific functionality in an existing C++ framework. Or one of the goals of the thesis might be to produce technical documentation to be published in a given format.
Other than that, leave them free to choose whatever works for them. Be clear and upfront about what you advise them to use, and what you are willing to teach them (and what you cannot teach them). For example:


  The choice is yours, as long as your are able to efficiently produce and edit a professional-looking 200-page document with many figures, tables, references and subdivisions, and it adheres to the university guidelines. I myself use LaTeX for writing articles and theses, as many colleagues, and I advise you to do the same. I have little experience with word processors. I can help you if you run into problems with the first one, but will not be able to help if you choose a word processor.


I once had a student who mastered MS Word to a level that I had never seen, and did a superb job in an efficient matter. It wouldn't have been bright of me to require him to use LaTeX when he knew another tool.