You would resort to physical violence because of an issue of free speech?
That makes you slightly better than the Charlie Hebdo killers, but not much better.
This.
Deal with it it like an adult and move on with your life.
Yes it's a bloke with a flag which represents terrorism, not free speech.
The United Nations has held ISIL responsible for human rights abuses and war crimes, and Amnesty International has reported ethnic cleansing by the group on a "historic scale". The group has been designated as a terrorist organisation by the United Nations, the European Union, the United Kingdom, the United States, India, Australia, Canada, Indonesia, Malaysia, Turkey, Saudi Arabia, the United Arab Emirates, Syria, Egypt, and Russia. Over 60 countries are directly or indirectly waging war against ISIL.
The UK is part of the global coalition working together to dismantle and destroy the threat of ISIL (Islamic State of Iraq and the Levant also known as Islamic State, Da’esh or ISIS).
ISIL is a terrorist organisation that claims to represent Islam, but it uses the banner of religion to carry out barbaric atrocities including beheadings, crucifixions, slaughter of children, selling of women as slaves and the systematic use of rape as a weapon.
So you think it's fine for him to do that without upsetting people and causing repercussions? on British soil?