Yes it is science; but it is also a leap of faith.
“Evolution” is an omnibus term including many components, from observed processes to grand theories, some of which have solid empirical evidence and some of which are mere hypotheses. Evolution as in “a change in allele frequencies in a population over time” is well documented with solid evidence, Evolution as in “Life on earth evolved gradually beginning with one primitive species—perhaps a self-replicating molecule—” has little supporting evidence and is a leap of faith.
What can you gain when you lose something? You can gain a new trait when you lose function. Desert mice gained black fur by a loss of function of the pigment regulation system. This was a beneficial loss of function mutation. So while your friend is not quite correct the general evolutionary trend is downhill, Darwin devolves. Nylonase has been touted as an example of evolution in a recent thread but ended with nobody trying to defend de novo evolution of Nylonase.
Many biologists have acknowledged the gap between micro and macro evolution. Consider microevolution as a change in allele frequencies in a population over time. Since this only involves changes in the proportions of existing alleles it can’t produce anything new; but if any allele becomes fixed then all other alleles for that gene are lost. There is no way this can ever add up to macroevolution no matter how long you wait.
The case of desert mice mentioned above is another type of micro- but since it came from breaking something previously working then continually breaking things won’t add up to macro- either.