||There aren't many things that apply today, because of our Globalization. Everything that we do can be explained as a commonly available alternative that is Kosher or allowed.
If someone cooks meat with milk, we wouldn't have to assume that he is doing a sin, we can say the milk is really "non-dairy," as is readily available.
If someone eats in a non-Kosher restaurant, we can assume he is eating those items that are OK.
If a person puts food in the oven or his air conditioner goes on in the middle of Shabbat, we assume that he has set them on timers.
On the issue of non-dairy milk the Kreity UPlaity says that Maarit Haayin does not apply if an alternative Kosher or permissable item is common, as in the above examples. The person who sees another eating meat cooked with milk can easily assume that this was "non-dairy" milk and the person was not doing any sin. The Halachah that prohibits it is only in places or times when non-dairy milk was scarce.