^^I don't think it should be too much of a problem if he stays relatively low key as the designer for Ferre (in other words, not as famous as someone like Karl). The majority of customers rarely connect labels with the people behind them. You'd be surprised by the percentage of people who actually knew (before the news coverage) that Galliano designed for Dior.
I think most Ferre customers will stay around if they like the clothing he makes, in spite of his reputation. I'd say that Nike customers are more aware of the whole sweatshop thing than Ferre customers are of John Galliano's scandal (or maybe even who he is).
Anyway, I hope this is true and I hope that this works out for him, because he really has a lot of talent and I can see him both suiting and revitalising the brand.