If someone shows up in your oshi's chat and starts causing problems, the WORST thing you can do is tweet about it. All they want is to cause a stir and get attention and you're giving it to them. If you're annoyed by someone disrupting chat, channel that into something productive for the community like fanart or clips or anything your skillset allows for, even just tweeting about how much you enjoyed the stream is plenty to help your oshi succeed!