YOU SAID:
cats have no friends because they are dumb
INTO JAPANESE
彼らは馬鹿だから猫には友達がいません
BACK INTO ENGLISH
They are idiots so cats have no friends
INTO JAPANESE
彼らはばかですので、猫には友人がいません
BACK INTO ENGLISH
They are idiots, so cats have no friends
INTO JAPANESE
彼らはばかだから、猫には友人がいない
BACK INTO ENGLISH
They are idiots, so cats have no friends
That didn't even make that much sense in English.