Is part of a class where the intent is to learn what it's like to be Hoh - I think this is fine even something that should be encouraged to be done (perhaps the students should wear a button/badge indicating that they are participating in an HL awareness program)
Also - for hearing family and friends of Hoh or Deaf I think this is also very helpful
In both cases the key factor is that the person must be respectful (not act like a jerk while using the ear plugs to help simulate HL) and must explain if asked that they are participating in a 1 day/1week etc program where they wear ear plugs in public to help them better understand what it's like to have HL that impacts one's ability to orally communicate etc.
I think it would be rude for them to "fake" being deaf by lying if they were explicitly asked if they're Hoh - especially by someone who is Hoh or deaf themselves (ie a signer or someone with hearing aids etc).
A good answer would be "I'm in a class where we are given opportunities to experience what Hearing Loss is like - and this week my assignment is to keep these ear plugs at home & in public to learn about being Hoh more "first hand...")
I can say that my dad had a REALLY bad ear infection and wax impaction (bilaterally for 3days and then unilaterally for another week) - this caused him to have about 20db hearing loss, on top of any "age related HL" he might have. He had trouble on the phone, in noise places, during the last week he had to be aware what ear he used for the phone, what side of someone he walked on etc ... in short - he became aware of what WE Hohs all know to be "daily life".
After going through that he was MUCH more understanding about what it's like not to be able to hear various sounds etc (and what "hearing is different than UNDERSTANDING" really means!)
Similarly I had my mum wear Ear Plugs around the house one day while she was trying to do various things like watch tv, vaccuum (and hear the doorbell/phone), cook (hear the timer from the other room) and most importantly talking ... my mum is VERY bad at talking to me (at me?) from other rooms - which I'm somehow magically suppose to be able to hear (I'm Hoh - with +120dbHL on my right!).
My "experiment" helped - at least for a while (5years later, it's time to repeat the experiment I think). She was much better about having CC on the TV, about being in the same room when she was talking to me etc - and had a better appreciation for the amount of hearing loss I have. I showed her a copy of my various audiograms from Kindergarten through present and pointed out each frequency and db level I was able to hear at and above ... then I showed her the package from the ear plugs stating that the reduced 30db when "properly inserted" (or about 20-25db when "typically inserted"). She was SHOCKED ... because she figured that her "demo" with the ear plugs was probably MUCH more Hearing loss then
I had in my "Hoh side" and maybe as much as my "deaf side" - not even close!
My "Hoh side" ranges from about 20db-45db depending on frequency on a "good day" to about 25db-60db on a "bad day"(sick, exhausted, Fibro flare etc).
My "deaf side" is +120db across all frequencies ... I'm able to detect things tactilely at about 70db, but as for actually "hearing" I'm off the meter (and by the time we get to 120db it HURTS).
I guess the short answer to the OPs question is:
Yes, it's a good thing...as long as it's done respectfully, not as a means of deceiving people for a "questionable purposes", and as long as the person if directly asked if they are Hoh etc will explain the situation in an honest manner.
I really do believe that the understanding, respect, and general "good" that a student/family member/friend is likely to gain from having a personal experience with mild/moderate hearing loss far out-weighs the potential misunderstandings that may occur.
I think it's not rude or disrespectful I think that They want experiment what deaf is alike! 
I cannot!!! I already gave up about 5 mins! 
