I cried on my first day of preschool.You're dragged from the safety of your home, you're forced inside an unfamiliar environment, you're faced with strangers and who knows what they are capable of.
Preschool is the foundation of how you approach new relationships in the future. It taught me that you don't get to choose who you meet, thus it's better to give everyone a chance than make a fuss about them before you really get to know them.
If you spend enough time with them and they still turn out to be bastards, then at least you know for sure. Be wary of all prejudice.