Tantrum protests are that involve some sort of mildly belligerent spectacle meant to embarrass a public figure. Glitter bombs are a tantrum protest. No one knows why a public figure was glitter bombed, pied in the face or whatever when it is reported, people just know that they were mildly bullied.
It doesn’t embarrass any public figure worth protesting. The brief, surprising interruption and spectacle serves to anger and energize that politicians’s staff and loyalists and it annoys people who work the venues because they have to clean up the mess. Most folks who see or hear about the protest decide that the tantrum protester is someone with time to waste and is limited to the ingenuity of a schoolyard bully. The tactic is the focus.
It worked for Tea Partiers in town halls because they sought to derail, not to build. Liberal political action requires a base of consensus and calculated action to achieve a new goal to improve social justice and/or the value or efficiency of governments function. Blasting people with props from the local costume store doesn’t seem to aid that cause.