The brand team might think that agencies are capable of doing some magic or that they don't have any other work to do than to pamper their brand only, hence, it's demands all the way and an inevitable incapability to request let alone be treating someone with respect. So point 1 is to be agreed upon with respect.
Point 2: Well ... NO! Your agency will always be paid peanuts in return for all the hard work and there are chances that reasons are found to deduct whatever is being paid. While you go an extra mile, your legs could be broken for taking that efficient walk of going that extra mile. So professionalism? What professionalism? There are chances it never existed in the first place.
Point 3: Making up that already worked up mind? No, don't even ask for that because a sentence said a moment ago will be contradicted with the next and yes eventually that too is the agency's fault.
Point 4 & 5: Take designing for that matter, it's always the agency that has a designer, how else would the brand team have the expertise of designing something without having a designer? Constant revisions are interesting for them, not the agency ... while not knowing how something is done, still asking for changes is a great way of wasting time. So a big applause for the geniuses!
Point 6 & 7: Oh being rude comes with the package, besides, why would they care about bad feelings? There might also be a total lack of appreciation coupled with deliberate bad feelings.
Point 10: Giving credit is out of the league when the brand might hire someone to invent issues in the agency.
Point 11: Hahahaha! Paying invoices on time?!?! You've got to be kidding ... the brand would want every task to be accomplished before time and paying on time does not match this criteria so beware. You might be made synonymous with a beggar in return for reminding about the payment.
Point 13: Despite good work done by the agency, the team could be feeling bothered about why they hired you in the first place and would be constantly thinking about saving the peanuts they are paying you, that too, not on time. The problem lies in not trusting and not allowing innovation. There are good chances that the agency knows a brand's target audience more than the brand itself because it is the one that directly interacts with consumers.
Point 15: Knowing what they want? oh well as they say, 'ignorance is bliss'.
Point 16: A contract is one main thing, however, irrespective of the fact that you have under committed and over delivered, you could still be treated with disrespect and lack of trust. It takes a very sane and decent client to respect your work. Some brands are respectful towards their agencies while some would be so full of ...
Here's an interesting writeup or maybe a love (divorce) letter from the agency for it's client: