why are people jerks to strangers

i hate that every time i start to feel good about humanity, something happens to remind me that people can be real jerks.

yesterday my mom had not one but TWO rude/prejudiced comments thrown at her while in and around my apartment building. my mom who is one of the nicest people i've ever known (and not just cos she gave birth to me) does not deserve anything rude to happen to her.

• she noticed some people coming towards the elevator right as the door was closing so she held the door for them. the older man (with wife and grandchild in tow) told her to go ahead without them. then as the door was closing, my mom heard the man say, "besides, why would she think we'd want to ride the elevator with her." wtf did that guy mean?!?! why wouldn't you want to ride the elevator with a smiling lady? jerk.
• she was waiting to cross the street to the art store across from my building. next to her at the corner was a group of three people speaking in spanish. (which, duh, my mom understands.) in spanish they talked about what they thought my mom was (what ethnicity), critiquing what she was wearing (tshirt and capris ) and whether or not she understood them talking about her. talking about her loudly AS THEY STOOD RIGHT NEXT TO HER. my mom said she ignored them but i told her she should have said, 'si, yo entiendo, groseros.' (or something more scathing as she actually speaks spanish well and i do not.)
  

my mom didn't even mention either of these things to me until late into last night when i brought up the fact that maybe boston isn't so bad as i originally thought it was. maybe it was a nice city with nice people in it. but APPARENTLY NOT. although, i'm guessing in both cases based on location of where i live, these people were not from boston. just jerks from somewhere else on our great globe.