Muhammadu Buhari; She Belongs to my kitchen, my living room and the other room

Nigerian President Muhammadu Buhari has responded to criticism of his leadership by his wife Aisha Buhari about her interview with the BBC while at a press conference in Germany, while standing alongside Chancellor Angela Merkel.  saying that she "belongs to my kitchen".

Mrs Buhari had warned that she might not back him at the next election unless he made changes to his leadership style. 

What is the irony of him saying his wife belongs to the kitchen, standing alongside Germany's first female chancellor.