I take issue with the "negative consequences" claim. The built in assumption is that bad guys will "get away with murder" if the duty to retreat is removed, but unpack that.
There are a pile of factors that are the burden of the defense to assert and defend to justify the use of force, much less deadly force, under standard self-defense law. All SYG does is remove an utterly subjective assertion about whether or not the defendent could have retreated. It leaves every more factual, more "either/or" objective factor untouched (initiated conflict, course of crime, disparity of force, etc).
Saying that "duty to retreat" is necessary, when all those other factors are available for challenge by the prosecution if they exist, does not speak well of the prosecution's case.
If the -only- fact of the case the prosecution feels they can effectively challenge is the most subjective, they simply should not be putting a presumptively innocent citizen through the time and expense of an indictment, much less trial, particularly given the well-known potential for even a successful defense to utterly ruin the life of the acquittee.