Size is a very subjective issue, but also objective. There are limits to how big or small a watch can be but, even it this case, if the owner likes it like that then he shouldn't do otherwise because some people expressed something different. Just giving a partial opinion as if it was a standard truth is very misleading in fact.
We can all "think" that a watch is or is not acceptable size-wise or fashionable or in good taste. We can have our thoughts based on what we believe is a set of accepted, pre-set norms. There are contemporary standards, linked to a certain period of time, a confluence of trend lead by the main actors of the aesthetical fields. So, a standard - about size- is set. However, as time goes by, the standard may evolve.
But going beyond the "thinking" it in the privacy of our own minds and being the voice that represents the masses is quite another. Each society and culture places its own standards on what is and is not "acceptable". That varies a lot from one culture/nation/person to another. What allows one person to stand up and make "judgment"?
More and more, people seem to tend to have more difficulties in understanding how subjective a matter it is. A standard from some specific period can evolve as well and once people are used to something, they don't change easily. One person's concept of "right size" can and will be different to another person's concept. Stating as some sort of fact that size must conform to some preset vision of proportionality just doesn't always work as a universal truth because we all tend to differ in how we make subjective judgments.