Turning your back on the flag of your country says a lot more than just a refusal to salute it.
These three Muslims shouldn't be in any European army during a war on Muslim terrorists, and adding more Muslim personnel in the form of imams doesn't make the situation any better.
But, this is the Austrian army we're talking about, so logical thinking is irrelevant.
Not for a soldier. Refusal to follow regulations as simple as saluting the flag is a big, red warning of other, potentially deadly, trouble down the road.