That was a really shitty example by Zoro because Ace ended up dead exactly because of this mindset lol. Couldn't have picked a worse example.
Well that is just 1 example he used, but he said some facts. Vivi's location is uncertain, going to Marijoas is fighting all the marines, going to Alabasta is useless. He said that if they have some good Intel, they can go to help, but right now doing so is useless. So then his example of Ace holds more power(a bit), she seems to have escaped, so let's just trust her and her power.