Posted 14 August 2012 - 04:34 AM
I think both your examples could be okay, or both could be offensive - it's really context-dependent. In an informal situation, where you're speaking with friends who either speak Japanese, or find bad Japanese funny if you're speaking bad Japanese, or otherwise are cool with it, then it doesn't matter what you do. When you start talking to people with whom you aren't so close, I think it gets dicier.
I'm having a hard time verbalizing my thoughts on the matter, so I'll say I think I'm of the opinion that if you're not speaking with friends, it's better to just pick one language and stick to it, and to pick the appropriate one for the situation. If you speak perfect Japanese, great, but if you're in a situation where other people don't speak it, or don't speak it to the same degree that you do, or where you don't know whether they speak it or not (or where you don't know whether they WANT to speak it or not), it's better to just use English - it's just not appropriate otherwise. It's like showing up to a formal party in a swimsuit. The swimsuit's not inherently offensive but wearing it at the wrong time can be.
If you're speaking bad Japanese, it's the same thing, but with the added notion that if people don't get the joke, it does reflect more negatively back on you, because not only is it not situationally appropriate but it also makes you look dumb. Basically, if you're not with people whom you know will immediately get the joke and find it funny, don't do it!
As an example, I studied Russian at university, and after some time together my classmates and I developed our own sort of Russian/English hybrid slang. A conversation might be as follows:
Me: Hey, Misha, mozhno your slovar' for a second?
Misha: Yeah, konechno.
Me: Spasibo. Hey, Anya and I were gonna get Chinese food later. You want in?
Misha: When are you going?
Me: I dunno, skoro.
It was perfectly all right to talk that way amongst ourselves, because we all understood it and were all in on the joke. If I had spoken that way to my professor, she would certainly have understood me, but she also would have thought I was lazy for not speaking to her entirely in Russian, when I was clearly able to make the effort to speak a few words. (She also would have ripped out my still-beating heart and used it as a chew toy as punishment for deliberately mangling her native tongue, but that's a story for another day...) If I had spoken that way to a Russian student not in my class, he probably would have assumed that I spoke Russian so badly that I could only use the few words I did. Had I spoken to him in flawless Russian, he might have thought it was great, or he might have been annoyed with me for speaking Russian when we both speak English natively and thus don't need to. If I had spoken that way to someone who doesn't speak any Russian, even if they had managed to understand me because of the context, they likely would wonder why I'm not speaking to them in a way they understand, which could lead to all kinds of unfavorable assumptions - that I'm a showoff, etc.
Pretty much, situational awareness is key. I think the reason that Japanese gets such a negative reaction is because anime fans are such a large group, and a lot of us do tend to have at least a little difficulty in reading social situations, so we're more likely than other groups to use foreign languages inappropriately.
As for the specific guy that was bothered by it, it sounds like a personal issue of his.