Jesus washed the disciples feet and the feet of Judas; so I guess it is alright for the Pope to wash the feet of Muslims. But can he tell the difference?
Jesus did not kiss anyone’s feet, but that is what Pope Francis does.
I’m no expert in these matters but it would seem reasonable to assume that Jesus restricted the procedure to his disciples, who were instructed to go forth and bring souls to Him.
The Holy Father, otoh, does not seek to convert anyone he washes — and whose feet he kisses — either before or after the procedure.
Washing = cleansing. A sort of baptism of the mission, perhaps. Kissing = ??