It doesn't work that way. I accept that zombies are possible because it is required of premise, just like I accept warp drive in Star Trek and that all the fat, stupid, working-class, infantile men in sitcoms have smoking hot wives.As I said, suspension of disbelief. As with any of this, you either "go with it" or you don't.
I do not, in turn, have to accept any stupidity they throw in there just because the premise requires me to suspend disbelief about something else. If some seagulls in "The Birds" started shooting lasers out of their eyes or crows started exploding like grenades, it wouldn't be acceptable to just say "oh well, the birds were already pretty unrealistic." There is a line that cannot be crossed and still maintain a credible set of rules.
As I said, "suspension of disbelief", you either accept the idea or you don't. This particular line doesn't work for you.
I don't have a problem with it. And to engage in "realism" arguments against it, when one could engage in any number of "technobabbleiean" rationals for it, to me, is unnecessary.
You either accept this particular idea...or you don't.
I do. You don't. It is that simple. No one else is required to measure this according to your own gauge.
I would be ecstatic if this was the worst "problem" of this film, which it is plain it is not.