I think it is impossible to know really. Morrissey is a monster to me because he is an overt racist, and supports actual facists, I guess I give more weight to intentions and beliefs than stupid mistakes. He isn’t that influential anymore but does have a hardcore following that dont see a problem with him, doubt he will radicalise many of them but probably feeds into the general anti-progressive ‘people get too offended nowadays, freespech, left going to far’ space.
No idea how to gauge the negative impact Siouxsie had, think it was before her band really took off, imagine she certainly influenced others to wear it, but think most of those would wear it in the same way she did, misguided shock fashion, of course that is bad in itself as it must be pretty traumatising for some people to see the swastika. I don’t think people get radicalised by stuff like that, it is the ideas of fascism that are seductive, offering easy answers, scapegoating, engendering a sense of false grievance and false victimisation on the believers. just can’t see Siouxie being the gateway to that, if she had accompanied it with right wing talking points i’d be less forgiving, as it stands I just think it was a stupid mistake.
But like I said, there being punk bands who used that imagery and then real nazi punk bands becoming a thing, feels like there might be a connection. I dont think it created those people and those beliefs, but maybe it made them think it was acceptable in that scene, think the subculture would have just manifest in a different way, racist meat heads would have probably invented punk by themselves. I don’t know, she doesnt pass my own personal threshold of dodge on account of being young, people make mistakes, and dont think she ever expressed rightwing ideas, and it is ideas that really spread fascism