The question is "should monkeys be available for research?"
You state that "we should use the best models available", therefore we should use monkeys for research. But this assumes that monkeys are available in the first place! It doesn't show that we should experiment on monkeys, just that we currently do.
unless you want to test drugs' safety on the actual best model available, they are the second best model available.
> that monkeys are available in the first place!
they are not available as in nature, they are bred to be available.
we're not going to some rain forest to capture them in the wild.
we could do the same with humans, in fact Nazis did it and it worked remarkably well, ethics issues aside.
Anyway, only a few thousands monkeys are used in trials and most of them in non lethal (they do not risk to die) trials, for a short period of time.
Most of the animals used are not primates.
Even assuming researches and pharmaceutical companies are evil and have the worst intentions, monkeys are the most expensive option and it takes a lot of times to breed them, a true evil entity wouldn't waste all that money and time, when a rat gestation time is 21 days and they mature in a few weeks.