Learn Spanish (Latin America): El perro tiene miedo y muerde. Acarícielo, pero es peligroso. - The dog is afraid and bites. Pet him, but he is dangerous.

When you attach a pronoun like lo to the end of a command, the word gets longer. To keep the spoken stress on the exact same vowel as the original verb (acaricie), we have to add a written accent mark. Without it, the rules of Spanish pronunciation would force you to stress the wrong syllable.

Why is it acarícielo and not acarícialo?

The speaker is using the formal usted command for the verb acariciar (to pet), which is acaricie. If they were talking to a friend using tú, they would use the informal command and say acarícialo.

Why is it tiene miedo? Shouldn't it use a form of the verb to be?

In Spanish, people and animals don't be afraid; they have fear. The phrase is tener miedo. You have probably seen this same pattern with being hungry (tener hambre) or expressing age (tener años).

If the dog is only biting because it is afraid right now, why does it say es peligroso instead of está peligroso?

Even though the dog's fear might be temporary, the fact that it will bite makes dangerous one of its defining characteristics in this context. We use ser (es) to describe these inherent traits of a person, animal, or thing.