What lady_disdain says.
If it's merely intelligent, the same way a desktop PC is intelligent, then I'd be polite so as to not get in the habit of rudeness, or to accidentally model rudeness when children are around. If it's actually sentient, or even sapient, then it can think and/or has feelings, and that needs to be respected the same way you'd respect other such things. Depending on it's level of sophistication, then, this would mean something on the spectrum of treating it kindly as one would a small animal to a child to another adult, and so on.
Saying, "It might be able to think, but it isn't biological/doesn't have a soul/etc." is the same excuse used for slavery and all sorts of horrible things throughout history, and it just doesn't hold water. If something can think or has feelings, then it needs to be treated accordingly, no matter what kind of system hosts its mind (biological, mechanical, virtual, etc.) I've always found films with robots being treated as less than humans/aliens/biological beings a bit distasteful. It's something akin to racism. Like in Star Wars and C-3PO: They just go and erase his memory (and R2D2's) at the end of episode 3, effectively lobotomising him, against his will. To do that to a person would be unthinkably amoral. Little things like that in otherwise good films always leave a bad taste in my mouth.