TL;DR: How do you fix a political question to avoid political biases
In this particular case you can utilize statements published by the President Of the United States via the Twitter Internet service to comport with
insist that opinion be backed up with facts and references
The below "tweets" are each attributed to "@realdonaldtrump" at the Twitter Internet service
The face of the Democrats is now Maxine Waters who, together with
Nancy Pelosi, have established a fine leadership team. They should
always stay together and lead the Democrats, who want Open Borders and
Unlimited Crime, well into the future....and pick Crooked Hillary for
Pres. Jun 26, 2018 07:36:18 AM
We must maintain a Strong Southern Border. We cannot allow our Country
to be overrun by illegal immigrants as the Democrats tell their phony
stories of sadness and grief, hoping it will help them in the
elections. Obama and others had the same pictures, and did nothing
about it! Jun 22, 2018 08:43:06 AM
My Administration is acting swiftly to address the illegal immigration
crisis on the Southern Border. Loopholes in our immigration laws all
supported by extremist open border Democrats...and that's what they
are - they're extremist open border
Democrats....https://t.co/F73I5gu0Q5 Jun 21, 2018 12:02:40 PM
It’s the Democrats fault, they won’t give us the votes needed to pass
good immigration legislation. They want open borders, which breeds
horrible crime. Republicans want security. But I am working on
something - it never ends! Jun 20, 2018 08:41:25 AM
Democrats are the problem. They don’t care about crime and want
illegal immigrants, no matter how bad they may be, to pour into and
infest our Country, like MS-13. They can’t win on their terrible
policies, so they view them as potential voters! Jun 19, 2018 08:52:24
There are two options available, either
The "tweets" by the President of the United States are considered to be false political rhetoric; not to be taken seriously; incapable of being vetted by way of fact-checking; or
The "tweets" by the President of the United States are considered to be true political rhetoric capable of being vetted by way of fact-checking.
If option 1. is the case, all questions and answers at Politics Beta containing any reference to what the current President of the United States has published should be placed "on hold" as being unequivocally false; "off-topic"; "primarily opinion-based".
If option 2. is the case, then OP is simply performing their political due diligence by fact-checking the actual statements ("tweets") attributed (there is plausible deniability involved here, as there has at least once been an occasion where the President's lawyer supposedly was attributed with a "tweet") to the President of the United States using the Twitter Internet service, without relegating the inquiry solely to the premise of a tone being set by the cumulative statements of the President of the United States and senior cabinet officials as to the subject matter of "illegal immigration".
Thus, relevant to this specific case, the user can utilize the statements of the President of the United States to either substantiate that statements made by the President are factually false, or factually true. Either way, fact-checking must be performed. To get to that point logic demands that the question must first be asked:
Is there evidence that the Democratic Party defends illegal
which OP did.
The result of the inquiry cannot be opinion-based. That does not mean that individuals will not apply their politics to the result of the fact-checking, and draw their own opinionated conclusions, irrespective of the facts.
It is up to the individual to determine what is fact and opinion, not other users or moderators, or the "site" itself.
The fact-checking process must be thorough, including answers from all perspectives, in order to gather as much evidence as possible for the purpose of determining truth, not limiting input to avoid the process of fact-checking in the first instance.