For me, self-expression is key, and I hardly stammer when I can just be myself. So if I feel chatty, I'll chat. If I feel jokey, I'll joke. If I feel introspective, I'll be quiet. If I'm annoyed, I'll say so. If I'm angry, well, I'll calm myself a bit before saying something I might regret, but will still express the feeling if I can while respecting others. The only time I might appear disrespectful to onlookers is when engaging in banter with friends or colleagues, but there's already a relationship built up where banter is understood to be playful within established boundaries, so it's not really disrespectful. If I stammer, usually I'm not authentically expressing myself for some reason (and those reasons are many and varied).