"when the entire Purpose of the rally is to protest something that they believe will be harmful to the environment"

 It wasn't, that's a lie.  The image presented and the information saying it was for the "Purpose" of climate change protest with Greta is a lie.  The Glastonbury Festival is not an environmental protest event at all.

 So saying this is evidence that a bunch of lefties had an protest about environmental issues and left trash around is completely false.  It's a lie.

 So why keep claiming it happened at Glastonbury?  Why not use information from an actual Protest event where trash was really left behind?


 This right here is the answer to your question: "IDK why people post a picture and attribute it to something and it is bullshit"

 They do it because it works.  You still treat this like it was an environmental protest event where trash was left behind when it wasn't that at all.  You were lied to.
 

"I didn't say it was. You holler liar a lot. Maybe you could try
Mistaken
Possibly"

 Citizen Free Press was not "mistaken" when they posted that and then immediately after post a link saying they have "proof" the image is not from 2015 and offered a second duplicitous source that is also completely false.

 The post you linked to is a lie, not a mistake.


"I've seen the disaster left behind at protests against pipelines and other things that lefties are against."

 I'm sure you have, and if there was a picture from a pipeline protest I'd be all about it.  But why use pictures from other events from 7 years ago where trash wasn't left behind to prove that point?

 It's like trying to let people know how great a Corvette is and showing them pictures of a wrecked Honda hatchback as evidence.  Why not show pictures of a Corvette?  

"And you say, 'RED Car', comparison is bad !"

 I said it is a poor argument specific to the task of changing minds in exclusivity with the exemption of all other known tasks.  

 What good does providing photos of unrelated events do to prove a point?  If I posted pictures of trash left at a Trump rally and they were really pictures of an unrelated event in Europe where the trash was picked up, what point would that image prove?

 It would only prove my source lied.

With everything that's going on in the world,... we're talking about fireworks and littering.
Is this what the fringe right feeds you?

Don't you know we're on the verge of a serious mustard shortage?  

You are surely putting groceries in your house, right? I mean, your fearless leader Said we were going to see food shortages.