(this will be longish!)
I did read about that march, but after the thread about the rise of the right was closed, i did not see where to post stuff about it, so thanks for this new thread Adept
One of the aspects of Nationalism that is always hard to stop, is that it is an 'easy' philosophy to spread, and it kind of gets to the crux of the issue why our evolution as human beings seems to have stalled. We have all this amazing science and technology around us, much of it could easily be leveraged to push us all to the next level on our evolutionary path; getting rid of poverty, providing clean and cheap (often free) energy etc.
But there is an 'agenda' at play in the world around us, one fuelled by control of 'old world' technologies (Oil, Coal, Mineral wealth etc) that also funds political influence and top level decision making. It has control of vast media empires and all this is, and has been for a good 20 years now, pushing a Nationalist mindset. It is the principle reason behind the rise of the right we are all witnessing, from Trump/Marie Le Penn to Brexit and these kind of marches.
As the dream of Neoliberalism faded, when people actually woke up to the fact of the wealth simply concentrating with a smaller group of people while the rest of us got progressively more poor, each one of us has had to face harder decisions to just get by in our lives (be it less holidays or having to buy less stuff that made us happy or at the other end of the scale simply having a harder time putting food on the table (in the uk food-bank usage is at an all time high)).
This can easily be turned into anger, and Nationalism needs an angry base to ride on. It just so happened that while the powers that be (the USA) decided to war in the oil-rich regions of the world, the displacement of the populations there was always going to hit Europe the hardest (it is the nearest 'safe' place), and for the USA this was a good thing, as it knew it could carry on undermining the 'left' aspects in the eurozone (i include the uk in this).
So the media outlets spread the lies (mostly) about this 'Islamic' influx, job stealing to etc. Obviously the terror attacks fed into all that (and were always going to happen, just as fallout from the West's wars in the middle east) and again the story could be shifted to increase the growing anger amongst the already angry populace.
'Foreigners' are to blame for all that ails us etc. It is a simple story for a simple mindset, one that then does not have to face the actual complexity of the real situation. You just turn it into a fantasy enemy that people can get behind resisting and being angry about. And the simplicity in the Nationalist philosophy is what makes it so dangerous, as has been proven time and again in modern history.
The only way to fight it is in education, and as we have seen across all our western societies where Nationalism has been resurfacing, state level education has been slipping, and much like with our health services is one of the corners of a civilised society that has been under attack.
So how to stop this trend. Simple. You just have to stop voting for the right, stop paying for it's media and tell the story far and wide on what is actually going on. That is if you want to live in a civilised society where we all enjoy a better standard of living (rather than one where it will only be the privileged few).
This is speaking as someone that has voted for the right in the past (to get Blair's power out of the Labour Party), but will not again for the foreseeable future.
And in specific reference to the 'Islamic' aspect of the current problem i highly recommend the 'Power of Nightmare' series by Adam Curtis:
https://en.wikipedia.org/wiki/The_Power_of_Nightmares
It's a very complete analysis of how we got here, and an easy-to-get-into launch point for further study
