We aren't talking about illegal vs undocumented (there's a strawman for you)
Slur's aren't defined by "partisans" but by intent. I don't believe anchor-baby has ever been meant as anything but a slur.
It certainly isn't a slur when I use it anymore than thief, robber, criminal, illegal, money laundering, mooching, capitalizing, forger, or jaywalker are slurs. I have people in my family named Chavez, Lujan, Vallejos, and Melendrez and they are all dear to me. And I would not hesitate to use the term 'anchor baby' in front of any one of them. I believe most if not all with Spanish surnames would use the term themselves.
To designate a term like 'anchor baby' as a slur by the PC police is not because it was a slur but is to MAKE it a slur. We are seeing this more and more as the Left continues to try to clean up perceptions of those who break our laws and make them into something acceptable, sympathetic, and make it politically incorrect to accuse or prosecute. It also is to give ammunition with which to accuse those who want the law enforced and our borders secure.
It isn't designated as a slur by any PC police. What is and isn't a slur depends on the intent. if you aren't intending it as a slur you're unusual - just take a stroll through these boards and see how it's used.
Thief, robber, criminal, illegal, money laundering, mooching, capitalizing, forger, or jaywalker all describe crimiinal actions of some sort, or criminals (accept for capitilizing). An "Anchor Baby" is a child who has done nothing wrong to deserve that perjorative.
It's interesting that everytime a slur is defined as a slur - someone gets all up in arms demanding their right to use that term any way they want without it being considered a slur. Things don't always start out as slurs - but, when they get used often enough to attack a person or group, they become slurs. Words change over time with intent.
I don't give a crap about what is PC and what isn't - and this is just a dictionary for gosh sakes, not some new law. But behind every perjorative is a real human being and it's easy to forget that in this sort of mindless hatred.