I use an MGW Sight-Pro with the correct shoes and have never had a problem getting sights off any handgun.
I tape the clamping surfaces of the slide with painter's tape, and use plastic shims on the press pads, tightening everything down so it won't move. At all.
Soak the sight dovetail in Kroil for a little while, tapping the area lightly with a brass hammer to help the Kroil seep in before applying steady, consistent pressure with the press.
Works every time, even on those godawful tight S&W dovetails.
Some dovetails are cut with a slight taper, and you have to make sure which way to push the sight out. My notebook back home has a list of models that I know of, and there's resources available on the Internet.
If he's telling you he's afraid of breaking something, he's probably using cheap tools or doesn't know what he's doing.
I'm almost tempted to open a shop in south Mississippi, after hearing all the horror stories about the state of Mississippi gunsmithing.