This is the Platonist vs Nominalist controversy. Do categories like “horse” exist in reality? Or are there only individual organisms we arbitrarily categorize as “horse”/”equine”?
I can see why you might confuse these two arguments but they are in fact subtly and importantly different.
I am not arguing that objective truths dont exist in reality (or that they do for that matter) at all. Only that if they exist you can never be 100% certain of something being an objective truth, therefore even if we accept objective truths as existing, anyone trying to state something is an objective truth is still stating an opinion that it is one of the objective truths that exist, and they could still be wrong about this. So regardless of if objective truths exist or not every utterance is always an opinion.