It's an anecdote about a common practice. Noting officially that someone who has broken the law is here illegally brings additional work and paperwork - and sometimes fed attention (which local officials may or may not want). In sanctuary areas, this is lessened because they refuse to cooperate with ICE, etc.
Even
inside the criminal justice system, data is incomplete.
Few local jurisdictions are willing to release data on undocumented prisoners, and in the case of sanctuary cities and states, this is deliberately in order to avoid federal eyes and not differentiate between groups in reporting. Another result of that is that we get lots of illegals who
do commit crimes, who then get to remain, regardless:
...A 2018 Government Accountability Office study found the problem particularly acute in sanctuary states. The average criminal illegal alien in California has six convictions, yet remains in the United States. According to a recent letter from ICE officials to Congress, there are 662,566 immigrants on an ICE
non-detain docket—that is, they have been accused or convicted of a crime but aren’t being deported, including 435,719 convicted criminals and 226,847 with charges pending. This includes 62,231 convicted of assault (15,811 of sexual assault) and 14,301 convicted of burglary....
etc., so on, and so forth. Catch-And-Release
does leave criminals on the street where they
do victimize more people.
You may benefit from reading both sides, on this one.
Nope. They already have the result that fits the presuppositions, and, you can't include data that doesn't exist. The data that
exists for them to pull conclusions from leads to the conclusion they want to draw.
How
would you extrapolate for "we know that these kinds of law-breaking events happen, but not how many"? The data isn't there to include, because it's never collected in the first place.
Again, it's like drawing up a list of all Democratic politicians who cheated on their wives, tossing in Trump's name at the bottom, and declaring that Democrats Are The Party Of Infidelity - my unwillingness or inability to include the full data going in means my result does not accurately reflect of reality.
In this case, I don't think we can say that - other than crimes associated with their status (which I do think should count) - illegal aliens are more or less likely to commit regular crimes, because the data is (deliberately) deeply incomplete.