When talking about these things if I do at all, the first thing that I'd require is to clearly define the terms, and then also acknowledge that we're dealing with subjective ideas, such as your criteria for something to "deserve" respect, and your criteria for what's considered art, which is different for everyone. This is meant to not talk in circles and to speak clearly, if we're going to be serious about it.
So the term is "content creation", what is it? Is it anyone that creates (or attempts to create) anything as a form of art (or for other motives, such as informative media) for others to see? Would Tolkien be considered a content creator? Based on the other responses, you're just talking about people on YouTube, Twitch, etc.
Now that we have that, what is our criteria for something to be respected? As mentioned, this is different for everyone. Mine could be that the person needs to be putting a moderate amount of effort and passion into it, and that it's honest work. So for example, a video/story covering an event or person, if they do it because they have a genuine interest in informing the public about it, is not just a cash-grab, and they're not negligent about actually discovering the truth (like having journalistic integrity, being unbiased and logical), then that could be respectable. We can expand on this, but let's leave it at that.
Now, what is art? Difficult term to define because it's also different for everyone, but I'll say that it's any work willfully created by anyone with the intent of expressing any form of beauty or sensation, and that has some amount of effort. Under this definition, it would mean that there's "bad art" and "good art" (and anything in between), depending on the beholder; so I can personally say that the usual painting of Joan Miró (which I don't like) can be art, but to me it's relatively "bad art", because I don't find much beauty in it, nor does it make me feel anything substantial, and that is my opinion, to someone else it can be "good art".
Going back to your examples, in order to put the analysis into practice: Markiplier making an "O face". I honestly don't even know this particular video, so I'll assume that it's just him making a stupid face in an attempt to be funny, in a low quality video (so like, it does not go beyond that joke, there's no skilled editing or message worth of addressing). Then, what's the question, is this particular moment "art"?
I would not even consider that art, bad nor good, because it seems to me that it's a lazy & quick way to appeal to the retards on the fanbase for a quick laugh, so maybe in that sense it's just an entrepreneurial decision to keep being on brand and appeal to your average moronic YouTube commenter, and generate views/comments. Because I'm using my definition, that's the conclusion, however to those people who got mad at you, maybe they have different criteria for what's art so they disagree with you.
Then, is Markiplier as a content creator as a whole (so not just in one particular video), respectable in what relates to his work or "craft"? Well, I don't watch him much so I don't really know, but if he's honest in his work and actually attempts to create something that he considers worthy, or that it can brighten someone's day, or if it falls in the very summarized criteria I gave earlier about this, then yes it can be respected, at least if he does this in the majority of videos or an amount that you consider sufficient.
Do I need to like his content for this? Not necessarily.
Another of your examples: e-thot/"tiddy" streamers. This is easy, what they do is not art to me, it's the most lazy content intended as cash-grabs and nothing else, lowest tier denominator. Is it respectable? Again, no, and mostly for the same reasons. It does not meet the criteria on any level for being anything other than an Internet whore trying to make money.
These are easy examples, but you'd just have to see if your own personal criteria is met, and decide. Because it's relative, some cases will be more difficult to analyze (like what if someone seems to be really lazy and uncreative in half his videos, and really skilled and passionate in the other half), but it all comes down to this.
