It is slightly more offensive to assume that .com + browser settings == english above the country you are originating from, if you aren't speaking english, anyway.
Choosing google.com instead of google.nl however is a clear choice. Setting the preferred language of my browser is an even more explicit choice.
How can honoring explicit choices be more offensive than assuming the visitor is an idiot who can't think for themselves?
No it isn't, .com is the global domain, not the english one.
Browsers are often configured improperly and it's not always practical to rely on them but it definitely isn't offensive to follow the explicit preferences sent by the browser.