Languages are defined by usage, not by some proscriptive description. It is true that "begs the question" is the name of a specific philosophical fallacy that has been discussed for millennia. However in English it is common to say "begs the question" where you mean "raises the question", and therefore that is acceptable usage among native English speakers. (I don't know where that usage came from, at a guess it is a shortened version of the phrase "begs us to ask the question". Anyways it is common usage.)
Now did you have a comment on the actual content of what I said?
The usage is correct. To beg the question is to ask the audience to accept a proposition stated in the question without having first provided evidence supporting the proposition. This is exactly what the OP does, where he states "if the proposition is true..."
