Grading drafts for one team but not the rest of the league is pointless. Ted Thompson may be c+/b-, which would be bad if half the GM's consistently hit A's every year in the draft, but they don't, the draft is too random in nature for any one team to consistently be excellent. What is the median average grade throughout the league? Without knowing that it's impossible to state with any credibility/certainty that Ted Thompson is above average, below it, or anything else.
Its fine to have a subjective opinion on the matter "I don't think he's that good" etc. Everyone is entitled to thier own opinion. However, when you state it as objective fact, and fervently repeat the sentiment ad nauseum without ever providing objective research to back it up (again, this would be grading every team in the league, over the same period, and comparing TT's grades to see how he compares) it is simply absurd.
Even if you do grade every team in the league, what you have is not an objective fact, its a well-researched subjective opinion. You're at the mercy of your own imperfection and bias, and one person's grade is not a large enough sample to come to a consensus. To accurately grade and compare GMs, you would need a large group of people grading every team's draft for the last 10 years or so, ideally these people would be industry professionals who hold/have held personnel positions (gms, scouts, etc) in the NFL. If you could make that happen, then it would be reasonable to claim that the findings are objective fact.