Should I write my master's thesis in English, as a non-native speaker?
The reasons I write all my work in English, regardless of the country in which I work, are threefold: 


The scientific community works in English
English texts are easier to reuse
English texts are easier to share and diffuse


Reasons 2 and 3 are effectively based on premise number 1. In terms of the ability to reuse my work, more often than never I might have to give a presentation, a talk or create a poster based on some report/thesis/paper I previously wrote. This scenario is  common to both academia and industry. When this happens I can easily extract sentences, keywords and figures from my previous work if all the text contained in them is in English, without the need to translate it.

Similarly a document written in English can be given to anyone and they'll be able to read and understand it without requiring a translation. 

Therefore if I were you I would write the thesis in English, and present it also in English. I don't think that your examiners will feel in any way threatened by this. Ever more so if you are a foreign student and Italian is not your native language. You should not be expected or forced to write and/or present in a language you are not that familiar with, if English is an allowed option.