We are not allowed to accuse any Muslim to be doing Shirk unless he openly says that there is another God with Allah, or practically worships some one else with Allah (SWT).
Any act which we don't accept from a Muslim can never make a Muslim as a Mushrik unless he believes in Shirk and it is out of our knowledge to know what is in his heart, so we must be careful before accusing a Muslim of doing Shirk.
Wassalam.