Neither up- nor downvotes require a reason, and this, together with the anonymity of voting, is an important part of the Stack Exchange model. You can find a good number of discussions around this if you look, but there is no point arguing about it. Partly this is beacause nobody on the site has the power to change it, and partly because argument is itself alien to Stack Exchange; you can if you wish put forward reasons to support your post, but other people's opinions do not require your approval, and indeed a poorly-phrased 'justification' may be perceived as whining and inability to accept criticism, and lead to further downvotes.
Closevotes do require a reason, but one of the commoner reasons is "off-topic; not about English within the scope defined in the help center". If you had actually believed that and checked what the help centre says, you would have found that ELU (and other Stack Exchange sites) do not welcome discussions or "seeking clarification"; clear answers are given to clear questions, and, ideally, the correct answer is accepted.
The reason you were given is thus sufficient.