It was alleged that bot nets would try and dilute politically motivated trends by blasting out a hashtag that was one letter off- for example #podasta instead of #podesta.

Then 'real' users who started typing would autofill with the false one and the topic would lose steam quicker. Of course, without knowing Twitters proprietary algorithms, this is all just anecdotal.

I'm not sure that invalidates the reasoning behind nuking hashtags driven by bot farms, which is clearly a practice that negatively impacts the practice. What you're describing sounds like a case for better discerning between bots and real users.

Depends if the spam was used to initially seed the hashtag or if it comes in after genuine discussion between real people.

To me it seems like two different cases that are easy to distinguish.