they will not criticize her bad influence since [they themselves are like this also]

or [they are like this also]. Do in need the word themselves in between and do i need to make influence as plural

You don't need the word "themselves."

depends on the sentace

To determine whether you need to include the word "themselves" and make "influence" plural, you need to consider the context and intended meaning of the sentence.

If the sentence is expressing that the people in question are not criticizing her bad influence because they possess a similar influence themselves, you can use either of the following constructions:

1. "They will not criticize her bad influence since they themselves are like this also."
- Here, by including the word "themselves," you emphasize that the people have the same kind of bad influence as the woman being referred to.

2. "They will not criticize her bad influence since they are like this also."
- In this case, you omit the word "themselves," but the meaning remains the same. It suggests that the people have a similar bad influence.

Regarding the word "influence," whether you keep it singular or make it plural depends on the intended meaning. If you are referring to the singular influence possessed by each individual, you should keep it singular: "her bad influence." If you want to express that the people have multiple influences similar to hers, you can make it plural: "her bad influences."

In summary, both of these options are correct and convey a similar meaning:
- "They will not criticize her bad influence since they themselves are like this also."
- "They will not criticize her bad influence since they are like this also."