I think one needs to make a distinction between grammar and spelling errors that are anomalies or exceptions within an otherwise articulate document, and more consistent inattentiveness to writing quality, or sheer ineptitude. If I had a nickel for every unintended use of “their” for “they’re”, I could probably afford a very nice lunch today, but thankfully not much more than that (well, maybe coffee and a snack later in the day!).
It happens. At a certain point, however, we begin to cross the threshold of mere error into what appears to us like ignorance. So, in a sense, it is often a question of the relative density or errors/gaffes that tips us towards being judgmental.
The rule applies to colloquialisms or speech mannerisms. I suspect most here would insert a “Like” or “You know” in their speech occasionally. I imagine the president himself does, too. But after you reach a certain density of these phrases/utterances, and they cease to become the pinch of saffron in a 4-gallon stock pot, and something more like the vegetables and soup bone, one’s speech begins to sound juvenile.