They aren't "undocumented immigrants", they are illegal aliens.That's true of literally any group. You could just as easily say "I'm fine with Rhode Island being wiped off of the face of the planet. That will reduce murders and rapes". The incidents of violent crime among undocumented immigrants in this country is actually quite a bit lower than it is for US born citizens.
We'd also be losing the benefits that come from having them here. They pay payroll taxes but can't benefit from Federal programs. So they're funding systems for other people to use them. It's estimated that they bring in over $11 billion in Federal tax revenue every year.
They also contribute about $1700 a year to the government while equivalent native born citizens contribute an average of $1300. Meanwhile Dreamers are twice as likely as native born citizens to start businesses, and over the next decade they're estimated to contribute $460 BILLION in economic productivity.
And about 28% of Fortunate 500 companies were founded or co-founded by the children of immigrants- many of whom were originally undocumented.
Despite the fact that there is a whole wing of folks who have decided to build careers out of demonizing undocumented immigrants in this country, they've actually been hugely important for our economy and are responsible- directly or indirectly- for many of our biggest companies.
So they're less likely to commit violent crimes, more likely to contribute to the economy while less likely to make use of Federal government programs, and their children have been MASSIVELY beneficial to our country. People don't like to talk about these things in political circles, but they are 100% true. We hurt our country by ignoring these realities.
You don't like the "illegal" part? Then come into the country the right way.