Hosts Dortmund ran out 4-1 winners in Tuesday's UEFA Champions League meeting between the two sides, but play twice had to be briefly halted due to flares and firecrackers being thrown onto the pitch by away supporters.
Galatasaray have already been charged by UEFA on one occasion this season, after similar incidents marred their defeat to Arsenal last month.
Kehl told Dortmund's website: "If Galatasaray fans throw missiles on to the pitch or even into other blocks, you are concerned.
"What idiots. Someone could be injured, perhaps children were standing there. All that preoccupies you, even if you shouldn't really be distracted.
"You could notice from the Galatasaray players that they were ashamed of the behaviour of their fans."
Dortmund's victory on Tuesday ensured their qualification for the knockout stages with two games to spare.
In contrast, Galatasaray sit bottom of Group D, having claimed just a solitary point from four matches.
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