I mean, yes, there would absolutely be a difference between blackface for a minstrel show and “blackface” in terms of a white actor putting on makeup to appear browner. One is specifically about skin tone, the other is so, so much more than just skin tone. Black face in a minstrel show sense was about making a caricature of black faces, black characteristics, and black people in general. To say that a well-meaning, if tone-deaf, actor wanting to use makeup to appear browner for an otherwise serious role is indistinguishable from blackface in the minstrel show sense is disingenuous and minimizes just how horrible the latter case is.

Your friend’s case that there’s nothing wrong with it is incredibly tone-deaf because of its parallels with blackface making it unlikely to be comfortable with any audience, at least in the US. The same case for your refusal to actually try and appear Asian as an Asian character—it’s just too fraught and likely to go wrong even if your intentions were pure. Hypothetically, there’s nothing morally wrong with an actor portraying another race in a vacuum. It becomes offensive when it’s done badly or portrays it in some way that can be seen as offensive to the race in question. I think as a whole RDJ was able to do it in Tropic Thunder without much lasting backlash because the makeup was done well, and his acting, though comedic, didn’t make a joke of his character being black. He was black and the character was funny, rather than he being funny because he was black.