TBH, it's not really just a problem with Hergé. European comics throughout the century are full of stereotypes, typically used for comedic effect, which can look bad from a modern perspective. Asterix, by Goscinny and Uderzo, is entirely built on stereotypes. So is Alan Ford, by Secchi and Raviola.

In reality, most authors were not particularly racist; they just leveraged stereotypes to get cheap laughs, which was socially accepted back then.

Back in the day any European would laugh on itself as a tradition. Spaniards did the same with the Bruguera School (Mortadelo y Filemón, Zipi y Zape...) making fun on both the state/power/society and the outdated traditional family values. The Zapatilla brothers (Zipi and Zape) were subversive long ago before Bart Simpson and made a good laugh on the 60's Spain. MyF were basically "Get Smart" and the Superagent 86 10 years ago in the 70's, showing up a backwards Spain compared to France and Germany and making fun on the shitty infra we had on everything while we tried to fight crime. Luckly, times changed a lot in late 70's/80's.