I have tried to rephrase the sentences as you told me. Can you please have a look at them?

1)Finally, in my opinion, the way to solve the problem is very simple and consists in treating people in the same way.
2) People’s attitude to ads has changed. Instead of switching channels to avoid ads people tend to watch them because they sell lifestyles, not just products.
3)Advertising shows its clients what they will become if they buy a certain product.
4) People who are dissatisfied with their lives can be easily persuaded to buy the products they see (advertised) on TV.

1)Finally, the way to solve the problem is very simple: Treat people the way we ourselves want to be treated.

"in my opinion" is unnecessary.
http://grammar.ccc.commnet.edu/grammar/concise.htm
Scroll down and read the section called Phrases You Can Omit.


2) People’s attitudes about advertising have changed. Instead of switching channels to avoid ads, many people tend to watch them because the ads sell lifestyles, not just products.
The main problem here is that you have "people" and "attitudes" and "ads" -- all of which are plurals. But you must make it absolutely clear which one of those antecedents "they" or "them" refers to.
http://grammar.ccc.commnet.edu/grammar/consistency.htm
and
http://www.towson.edu/ows/modulepro.htm


3)Advertising attempts to show consumers what they will become if they buy a certain product.

4) People who are dissatisfied with their lives can be easily persuaded to buy the products they see advertised on TV.

Sure! Here are the rephrased sentences:

1) In my opinion, the solution to the problem is quite straightforward - treating people equally.
2) The way people perceive advertisements has shifted. Rather than changing channels to avoid them, people now tend to watch ads because they promote lifestyles and not just products.
3) Through advertising, clients are presented with a vision of the future they can attain by purchasing a specific product.
4) Individuals who are unhappy with their lives can be easily influenced to purchase advertised products they see on television.