Well, you jumped into the discussion with an assertion, not me. So I'm not sure it's you who establishes the parametres of this discussion. But let me tell you what I think about what you said...
I'm talking about the simple fact that one can not outright state something is the correct way of speaking, Cicero most certainly had a different accent to Caesar, the Romanised Gauls another etc. Do you alter your accent based on what text you're studying? Juvenal is different in so many subtle small ways to Cicero. The fact that we struggle with so many elements of prosody only compounds matters.
I don't see your problem here. When I read French literature I don't pronounce it with a different accent according to what accent the author had obviously, why should I do it for French? And still there are certain ways to pronounce French right (the way native speakers would pronounce it, including different accents) and others that are wrong, like if I think that A sounds like U, then I will pronounce French WRONG.
There is NOTHING, nothing so ugly to my ears as the Germanic accents many Anglo and Germanophonic scholars use when pronouncing Latin and Greek and claim is accurate because they have some idea about vowel length. There's much more to it than a few letters on a page. Unless you're naturally good at accents, or grew up multilingual, you're unlikely to be very good at pronouncing it. In my experience those protesting the loudest over the "correct way" are often amongst the worst.
At least in the academic area it's important to have common rules. When I don't understand what someone says to me because they think digitum is digit+um, it hinders communication. When people can't pronounce Latin, they blush in class because they think pinus is pronounced penis. Yes, that happened in a Latin class I had in England. Lovely. It's important to teach people how to pronounce a language so they can understand each other. Have you never spoken to someone who learnt English and used a word they pronounced wrong so you had no clue what they were saying? Where's the difference?
On the next level there is a problem with how we ourselves pronounce it: it's alright trying to distinguish between /w/ and /v/ but the Latin versions do not equate with our ones. There are so many variations of /r/ so which do you choose? Likewise with vowel length, we rightfully distinguish between short and long vowels but the actual quality of an /a/ can vary heavily.
Only because there is no v-sound in English that doesn't correspond to the Latin V, that doesn't mean there is a problem? There is no TH sound in German, that doesn't mean I have to be unable to pronounce the TH for the rest of my life. You can learn how to say the U continuer or how to say Loch Lomond.
I don't understand what you mean for the R.
Only because vowel lengths can vary after the distinction of long and short vowels, that doesn't affect the distinction. Surely it makes sense to distinguish between solum "alone" and solum "floor", whether the long O in solum is longer or shorter than the one in mos.
I would never tell anybody they were "wrong".
Well. In short: I would.
I'm not saying the poor grannies in the services have to stop saying gent-ass, but Classics students ought to make an effort.