Well I make my presumptions based on applying for and holding down jobs, knowledge of company policy and behaviour, and my knowledge of the agenda of some parts of the muslim community.
Of course you arrive at your conclusions based on your life experiences. But we don't all share the same life experiences and most are very, very different to yours.
Also, remember that you (maybe not you specifically, but you, collectively.) criticise some for having jobs, then attempt to suggest that certain parts of our community are spongers and don't/won't work. You appear to want to rant in all and any circumstances. I haven't searched your particular posts to suggest that you personally fit this criteria. As I have stated, my accusation was pointed at you all, well most. Sorry if I offend anyone by including them in that collective.
(Sorry, I'll edit that further by saying that some have this attitude, not all, not most, just some.)
..../This is all evidence, and it's reasonable to make some presumptions because it's not possible to have every single detail.
It's not evidence at all, for this subject under discussion, it's your life's experience. You have "decided" to commit to your memory in order for you to make sense of your world. I don't say that you/we have made a conscious decision to remember the details that you/we do remember but it's what makes our prejudices what they are.
......../Discussions normally proceed on the basis that assumptions are fair and reasonable or have proof to the contrary. You can either provide proof that MnS did plan all along to have a clumsy policy of swapping staff out at checkouts if pork came along the belt, or in the absence of proof to the contrary you can accept the reasonable presumption that it was an afterthought.
Not all, it's not necessary to make any assumptions in such episodes, it's sensible to wait for further evidence to arrive at a fair and reasonable conclusion. If you feel the need to rush into an assumption, then so be it, but that's you.
If you make an assumption that such and such a thing is just so, unless there is proof to the contrary, then you must believe in God, unless there is proof to the contrary!
To all those who wish to explicitly lable others with terms such as "over-educated, patronising leftie", remember that you are also implicitly labeling yourselves as the opposite, hence, "poorly-educated, over-bearing fascist".