I don't think anyone was ever physically assaulted in Bangalore for not speaking Kannada. Heckled yes, but bashed/thrashed/assaulted hell no.
I am an outsider too and my kannada is one of the worst. My local friends acknowledge that- it's just that I am not even good with my own mother tongue. But that aside every time I interact with a local - cops, babus, drivers, villagers in my halting kannada, trust me I sense a genuine acknowledgement from them at my attempt and I get my work done without any hassle. Thats all they look for - an acknowledgement that their culture and language also exists for people beyond their boundaries of ethnic construct. While yes there are outliers like anywhere, but people don't bash the other person for speaking Hindi. As already pointed by other people in audience here, not unlike in Pune. And definitely not unlike in Chennai, people bashing Bangalore have clearly not experienced how much worse hindi speakers would be treated there even 10 years ago.
And that actually applies to any society in the world where ethnic languages are spoken - be it French, Mandarin or Swahili.
I say this to my kannadiga friends as an outsider that what's happening now is that for most outsiders Bangalore is a gateway to South India. Had they been to Chennai and then come here, then things would have been viewed differently