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if we assume that Kizaru is taking this seriously, however briefly, then it might imply that at least Ben Beckman can somehow imbue bullets with Haki or at least his firearm has some capability of harming a logia user. We might extrapolate to say that Yasopp probably has a similar ability as the crew's marksman.
The ability to imbue projectiles with haki would also make it more clear as to why several of the captains under Whitebeard are shown to be using guns, despite their apparent uselessness against most strong characters in the series by this point, something I've always wondered about.
In any case, yeah, Yasopp and Marco all the way.
Having Haki, especially when it comes to top crewmember of a Yonko, is a given and there's no need to discuss, now the question is : What type of Haki does he have ? How proficient is he in each of them ? Those are the questions we cannot answer because we've seen nothing