Here are a few points I would consider in this discussion.
Firstly on safety wise most movements if performed well can be very safe. Dumbbell bench press and so forth if performed competently are suit this category. Dumbbell work can result in a more fuller range of movement which can be great for, flexibility hypertrophy but in some instances can exacerbate some joint problems.
Another interesting point I would like to mention is that if this exercise is executed throughout the training career it should manageable in a ME condition. This point relates to the amount of stabiliser muscles recruited and that if a highly trained individual were to use this exercise and not have gradually developed these stablilising muscles than injury could be prevalent.
My second issue I would consider, and Dave Tate makes this point as well, is that beginners should be trying to utilise the repeated efforts to a higher degree. This is to both learn the movements (important for non powerlifters as well) and also to better develop and hypertrophy the required musculature. I mention the last point with full knowledge of the ME ability to elicit hypertrophy.
Last I would like to conclude with that although loading is sometimes hampered the balancing effects some dumbbell exercises can more than make up for downfalls.
We are all dynamic creatures and so should our training be. In this vein of thought I would propose that these exercises be pursued throughout ones career and practiced in a variety of ways
Yours sincerely Physical Culture
Long Live The Body Science