It's a very reasonable fear, considering how pervasive and terrible Islamophobia is. They have a real chance of being physically attacked.
In a true act of allyship, non-Muslims in Australia have started using Twitter to offer to travel with Muslim individuals who don't feel safe going out in public alone. These people are offering to protect them should they be attacked for being Muslim because bigots have decided that all Muslim people are bad and deserve to suffer.
They started the hashtag #IllRideWithYou. It was specifically started by this woman:
Maybe start a hashtag? What’s in #illridewithyou?
— Sir Tessa (@sirtessa) December 15, 2014
From there, people started putting stickers on their bags and tweeting pictures of themselves with the hashtag so that nervous Muslim individuals could find them.
This is how you ally.