I understand that Merton was writing as a social scientist, and from that perspective it surely makes sense to take a norm as a way of capturing either an accepted regularity in social behaviour towards which people in the social community under study orient their action, or a rule of social behaviour which people in that community typically regard as binding. I will deal separately with questions about the norms that scientific communities typically recognise as binding in principle, and the way that scientists actually behave given the career-interests etc to which @Drux draws attention.
Regarding the norm of Universalism, @Drux says "I cannot believe that it is possible to have someone completely ignore all of their personal attributes and social background. Even further, I think that it is not necessarily a bad thing to let these factors affect your scientific ideas." There are certainly some philosophers who claim that a scientist, qua scientist, makes value judgements; one example given is that when doing statistical hypothesis testing a scientist may use a significance criterion of (say) p<0.05 to reject the null hypothesis where the consequence of doing so will be purely intellectual, but stronger criterion of (say) p<0.0001 where life is at stake, e.g. in a drug trial. But this seems to me rather different from allowing personal values to bias your scientific results, and therefore I do think that failing to keep the distinction clear between one's personal values and one's scientific commitments can be very harmful to science.
Part of the norm of universalism is that scientific investigations should be reported in an impersonal way; this is one of the reasons why we generally frown on the use of the first person in academic writing. It is interesting that it is, however, quite acceptable to use the first person when speaking about one's research. This shows, perhaps, that scientists embracing the norm of universalism are not under the illusion that they or their colleagues are impersonal robots: they are able to make the important distinction between personal preference and scientific judgement.
Regarding Disinterestedness: @Drux says "it is impossible to not act in self interest in terms of your career. This is the way you support your family and cement your legacy..."
This is an important point, but I think well answered by @Robert Bristow-Johnson in his reference to Lee Smolin ("career interests have actually eclipse the interest of real science"). We could take Continental Drift as an old example of this (there was strong resistance to this theory in America, because it did not suit the career interests of oil geologists) and we could take Climate Change as a more recent example, where nearly all the scientists who doubt that human activity is causing global warming are in positions where they don't depend upon research grants from e.g. IPCC.
I prefer to take no position on Climate Change as a substantive issue. The "climate scientists" have abandoned Mertonian norms, but that does not mean their results are wrong in fact. Vice versa the "climate sceptics" don't publish in peer reviewed journals, which seems to infringe universalism. Some allege the institutions of science have been irretrievably corrupted. Perhaps @Drux is right and the Mertonian norms ask too much of frail humanity!