John Harvey Kellogg, M.D. (February 26, 1852 - December 14, 1943) was an American medical doctor, nutritionist, inventor, health activist, and businessman. He was the director of the Battle Creek Sanitarium in Battle Creek, Michigan. The sanitarium was founded by members of the Seventh-day Adventist Church. It combined aspects of a European spa, a hydrotherapy institution, a hospital and a high-class hotel.

Though alcoholic beverages were commonly used a stimulant by the medical community during the time that Kellogg began his medical practice, he was firm in his opposition to the practice. The usage of alcohol as a remedy to anything was "an evil of stupendous proportions."  Kellogg went against the prevailing notion of the time that alcohol was a stimulant. Citing contemporary research, Kellogg believed that alcohol could not be a stimulant because it lessened vital activity and depressed vital forces. Seeing its effects on plants, animals, and humans, he felt that alcohol was a poison. Kellogg noticed deleterious effects that alcohol had on both the brain, the digestive system, and the liver, among other organs.  In addition to the idea that alcohol was an unsuitable therapeutic tool, Kellogg also considered it to lead to mental and moral bankruptcy. Alcohol was "one of the devil's most efficient agents for destroying the happiness of man, both for the present and the hereafter." Even moderate drinkers were subject to these effects, as Kellogg felt that a poison was a poison in all doses.  Kellogg also opposed tea and coffee due to the caffeine content of those beverages. His view was that caffeine was a poison. Not only did he detail numerous physiological and developmental problems caused by caffeine, but he also suggested that caffeine usage could lead to moral deficiencies. He blamed the prevalence of these beverages not only on the prohibition of alcoholic beverages at the time, but also on the extensive marketing efforts organized by the producers of these products. Kellogg's view was that "nature has supplied us with pure water, with a great variety of fruit juices and wholesome and harmless flavors quite sufficient to meet all our needs."  As early as the 1880s, Kellogg had prepared charts and lectures on the dangers of tobacco and alcohol, which were used widely by lecturers who encouraged temperance in their students. In 1878, John Harvey Kellogg, along with Ellen White, the founder of the Seventh-day Adventists, and several others, had organized the American Health and Temperance Association. The goal of this organization was to expose the far-reaching dangers of tobacco, alcohol, tea, and coffee. For the 15 years that the organization persisted, Kellogg remained as its president.Answer this question using a quote from the following article:

What did he feel was bad about using caffeine?
His view was that caffeine was a poison.