This sort of rationalization has become so commonplace that many view the act in an innocuous manner. Is taking a hotel towel really stealing? And what does this have to do with this week's Torah portion?
וַיֹּאמֶר אֱלֹהִים לְנֹחַ, קֵץ כָּל-בָּשָׂר בָּא לְפָנַי--כִּי-מָלְאָה הָאָרֶץ חָמָס, מִפְּנֵיהֶם; וְהִנְנִי מַשְׁחִיתָם, אֶת-הָאָרֶץ.
"And G-d said to Noah, 'The end of all flesh has come before me, for the earth is filled with corruption." -Genesis 6:13
It sounds intriguing, but the connection between hotel towels and Noah is not quite there. What sort of corruption are we talking about here? The text is vague as to exactly what sealed humanity's fate. In the Talmud (Sanhedrin 108a), Rabbi Yochanan said that Noah's generation did themselves in when they were guilty of stealing.
There is also an interesting Midrash (Braishit Rabbah 30) regarding one of the words used, חָמָס. In the Midrash, חָמָס is defined as stealing less than a פרוטה, which was not punishable back in those times. This would be analogous to somebody stealing a penny. A small, insignificant amount, right? Even if it is infintensantly small, the Midrash has something to say about this. During Noah's generation, there would be a man who had a box of beans to sell. When someone came along, they stole less than the worth of a פרוטה. However, when enough people walked by, the man was left without any beans, and he couldn't prosecute anybody because the monetary worth of the theft was so minute that he couldn't recuperate from his loss.
There is truth to the phrase "character is what a man does when no one is looking [except G-d]." This seemingly harmless behavior led to a slippery slope of that behavior seeping into the public. It is no coincidence that G-d points out in Genesis 6:11 that this corruption was לִפְנֵי הָאֱלֹהִים (before Him), meaning that it was out in public.
Many rabbis have interpreted the fall of humanity during this time period to be attributed to theft, and it should be self-evident as to why. In reality, it's much more than a hotel towel. It's a statement about character. Whether it's a towel or a $100 bill, you are the taking of the property of another without the owner's consent. Stealing is still stealing. Justifying the theft of the towel has the grave potential of being able to justify the theft of stealing that $100 bill with the same ease.
G-d made it clear with the covenant in the form of a rainbow (Genesis 9:13) that He will never flood the Earth again in such a matter. However, we need to be mindful to conduct ourselves in such a matter so we can avoid the spiritual decline that humanity experienced pre-Flood.