So you wait till you have a Yankel Rosenbaum before you say, "now this, this! This a pogrom!"
Very simple. One guy does that, and he is ostracized, not a pogrom. Anytime, it's acceptable and you can have multiple people as a group doing that impunity, it is a hair breadths away from shefichas dumim.
Hyperbole serves no one, it merely serves to water down the word. Call it out right away and try to put a stop to it but don't call it something it isn't. I agree with
@Randomex on this one if the definition is false.
Although you can hear both tzdadim. Wordweb says a pogrom is:
Organized persecution of an ethnic group (especially Jews)
How do you define organized? I would assume that multiple people doing this because they feel like it falls short of the definition (albeit slightly) - pogroms in the past had that tacit approval of the local authority.