If you're asking that question you need to simultaneously ask it for Christianity, Buddhism, Judaism, Sikhism.... et al...
I have many muslim friends - who are aware I am Catholic - and have taught many students who were muslim, but none of them would pray on a bus.... seems a little strange. They must be very devout to feel the need to pray at the exact time they were on the bus, as muslims I know would wait as they believe God / Allah would understand that you know, buses are sometimes late and you may be a bit late getting to mosque. My students, all of them were so lovely, would politely ask if it was ok for them to pray - in my classroom, during breaks - of course I said yes, and that they didn't need to ask, but they did every time and I asked if they wanted me to leave out of respect and they were happy to continue with me marking and setting up the class.
If he was praying to himself - aka murmuring the prayer - it would be seen culturally in the UK as a bit strange and out of place - we often associate prayer within a specific building or in private.
However, I would indeed find it strange if he was full on praying, including the kneeling and bowing if it was in the aisle of the bus. If he was just saying his prayer - I can understand some people's apprehension, especially as the words of prayer have been misused by Extremists and Terrorists - which is an important distinction to make - where they use the words of Allah to suit their own agenda - you just have to watch something like 24 or Homeland to understand what I mean - there is a phrase from the prayer (I believe, unless I confused my student's meaning) that is chosen before they commit certain acts. As I said, the apprehension considering the previous experience of London buses in July and some Extremists and Terrorists - past events by idiots tarnish the reputations of good, honest, loving people who are as equally appalled by the actions of terrorists as we are.
People will laugh and ridicule things they A: do not understand = ignorance B: Are afraid of (thank you media!) + don't understand = crowd mentality - this is what every extremist clings to whether they are Christian extremists - KKK, Muslim Extremists - Al Qaeda etc, it's the same mentality that was used to justify slavery, Nazi propaganda, apartheid -
I had a student who was the kindest, loveliest and most generous woman I have ever met. She was always polite, friendly, courteous and CHOSE to learn English in order to help her children through school, communicate with other parents and to become part of society whilst her husband finished his master's degree.
She came into the school one day, literally distraught, and told me how a man had pushed into her, yelled at her and spat in her direction and said bad words to her. He had shouted about her wearing her hijab and nikaab (headscarf and veil) - bearing in mind, this lady wore European clothes, not a burqa- and basically told her to 'bugger off home' for wearing a burqa.
She hadn't understood why when she had done nothing wrong, why he was being disrespectful and my only answer was he was an uneducated idiot - may not have been wholly his fault, as he didn't understand - I also then explained how in the UK and many other countries - covering your face is seen as 'hiding something' as if you are a criminal and how people culturally associate not being able to see someone's face as untrustworthy - she was literally blown away.
She explained to me how she covers her hair because it is in the Qu'ran and it is a sign of respect. She also insisted she chose to wear the nikaab in public, as she only shows her face to those she trusts, her family, friends and her teacher (me) because it was showing a part of emotions on her face, so it was showing her 'full self' - and I thought this was such a lovely way of explaining it. She also added she wears western clothes as she wanted to show she was willing to integrate, whilst still keeping her religion sacred, but showing she accepted and understood European culture too....
Religion will always be a source of conflict, and there will always be extremists and people trying to scaremonger - whichever side they are on - and always will be people who are rude and disrespectful.
All we can do is show respect to others and hope it passes on, sharing respect and cultures and just being nice to each other.... I literally knew nothing about muslim culture and customs, but it was so interesting to see - wait for the trolls! - similarities in my religion - in all religion, which is what extremists miss, of love and respect for one another....
I just think the world would be so much nicer if people would listen to each other, share their differences and similarities and respect one another.... but maybe I'm just an idealist...