> this report at a glance has some issues.

I don't think you actually read the report, but if you had, you might have seized upon a few limitations imposed upon this study. Consider this statement, which appears on page 9:

The vast majority of the incident reports considered,
however, did not consistently and systematically document
information in such an easily transcribable manner, instead
communicating or expressing answers—if any at all—to the above questions in a textual narrative (often located at
the end of the incident report). It is, of course, relatively more difficult to generate a categorical variable from purely narrative text, and, in particular, one must decide how to deal with narratives that are silent or ambiguous with respect to one or more of the questions posed above.

Or, there is this statement, which appears on page 11:

By examining impact rates, it is possible to control for racial disparities in the underlying populations impacted by SWAT deployments. Rates are expressed in terms of individuals impacted by SWAT deployment per 100,000 individuals. In particular, to calculate the white, Black, or Latino SWAT impact rate in a given jurisdiction, the number of white, Black, or Latino individuals impacted by SWAT deployments is divided by the total white, Black, or Latino population in that jurisdiction; the corresponding ratio is then multiplied by 100,000 to obtain the impact rate per 100,000.

There is more information on the data that the ACLU collected starting on page 27. Consider this statement:

The ACLU filed public records requests with more than 255 law enforcement agencies during the course of this investigation. One hundred and fourteen of the agencies denied the ACLU’s request, either in full or in part.

They assess the quality of the data received as follows:

The records that were produced revealed an extremely
troubling trend: that data collecting and reporting in
the context of SWAT was at best sporadic and at worst
virtually nonexistent. Not a single law enforcement agency
in this investigation provided records containing all of
the information that the ACLU believes is necessary to
undertake a thorough examination of police militarization.
Some agencies (e.g., Tupelo, Mississippi) provided
records that were nearly totally lacking in important
information. Others (e.g., Salt Lake City, Utah) provided
records that were quite lengthy, though still incomplete
and extremely difficult to analyze because of their lack of
organization.

Or their conclusion:

This variation has two immediate results: (1) any analysis of the data will necessarily have to contend with a large number of unknowns (as demonstrated above) and (2) it makes
systematic, thorough, and uniform collection of SWAT
data, at any level of government, impossible.

The ACLU acknowledges the flaws in this report, both in the body and in their section on methodology. And, they provide some good reasons for these flaws.

On the topic of race, consider this 2008 table of incarceration rates for 100,000 in Utah. (source: http://kff.org/disparities-policy/state-indicator/incarcerat...):

All men: 428.0
White: 347.7
Black: 2696.9
Hispanic: 664.6

There is roughly a 9x difference in incarceration rates (expressed per 100,000) in Utah in 2008. Now, the ACLU report gives numbers on three different cities in Utah.

In Ogden, black people are 39.55 times more likely to be impacted by SWAT actions than white people. In Unified, black people are 10.33 times more likely to be impacted. Meanwhile, in Salt Lake City, the number is 7.33 times.

Again, I'll remind you of this statement, which can be found on pages 9 and 10:

It is important to note that the data analysis in the report does not seek to make statistical estimates about the larger universe of SWAT deployments nationwide. Rather, the analysis is descriptive in nature, providing a general picture of SWAT deployments for this small cross section of
otherwise randomly chosen law enforcement agencies—the
information contained in the documents received is not
used to make more general, broader statements about the
use and impact of SWAT nationwide.

It is difficult to criticize a report's methodology when the authors acknowledge the shortcomings, explain why the shortcomings exist and try to express the data they receive in as diplomatic a matter as possible. Consider that this report is not meant to provide a statistical analysis on the state of SWAT in the United States. Rather, it is meant to 'shine a bright light' (to use their term) on militarization that has occurred largely without any public oversight.