[reordered]
>I also feel very Dresden-challenged after reading this... something about sandbags, measurement... I understand most of (the pieces of most of) the words, yet when I try for the whole, the balloon pops and I get nothing. So... curiosity itches.

Lutz already translated the background picture of PEGIDA and its strong [numerical] connection to Dresden.

>>Sandsack-Schonungsmassnahme,
describes the scenario of a newly converted islamic Thomas meeting some of the anti-islamic, right-wing and probably somewhat violence-prone parts of PEGIDA as part-intentional to give the heavy bag time to recuperate

>> solange nicht zu viele auf einmal kommen...
but only if not too many of those hooligans turn up at once

>>Aber die Ballung/der Schwerpunkt bei Euch

harks on the fact that those demonstrations ONLY in Dresden have headcounts worthy to report and are held repeatedly. There were quite a few attempts to establish such demonstrations in other cities, which mostly fizzled or were met with anti-(anti-islamic) protesters having more supporters.

Even stipulated that former east-german areas see demonstrations from '89 expirience different compared to those from former west, in Leipzig (the other former pure east city of size) there was a (in numbers 1 as of now) large turnout , but balanced/off-set by anti-(anti-islamic) protesters of greater head count, if the reports and countings are to be trusted.

>> ist auch für nicht-dresdener Deutsche erklärungsbedürftig
This discrepance is really puzzling, not only for foreign press, but germans living not in Dresden, even if they are not in any political machine but interested in such penomena.