Sunday, May 18, 1919

Fair.  Cloudy and bright at intervals.  To Church and S.S.  Played & read in P.M.  To Epworth League.  To First Baptist Church.  Good sermon on SMOKING.  Home.  To bed 10:30 P.M.  Thankful for friends.

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I would guess that Stanford was against smoking in the same way he was against drinking.  The habit was apparently becoming a concern by 1919, especially after World War I. According to one website,

by the 1900s cigarette smoking was a national issue. Concerned citizens formed anti-smoking groups, women were arrested for smoking in public, and government officials attempted to pass anti-smoking legislation. 15 states had a ban on cigarette sales in 1909, and it looked like the anti-smoking forces were winning.

In the 1910s, the tide began to turn the other way. Anti-smoking groups were ridiculed and anti-smoking laws were repealed. The introduction of the first book matches in 1912 made smoking easier than ever. The first modern, nationally-advertised brands went on sale during this decade....Camels, Chesterfields and Lucky Strikes.

Then came World War I. Cigarettes were handed out to the soldiers as part of their rations, and anyone who opposed this practice was labeled a traitor. A whole generation of young men came back from the war addicted to cigarettes. 

Capitalizing on that addiction, cigarette ads portrayed happy service members lighting up.  Here's one ad from 1919:

A quote from General John J. Pershing makes it crystal clear:

You ask me what we need to win this war. I answer tobacco as much as bullets. Tobacco is as indispensable as the daily ration; we must have thousands of tons without delay.

And in order to make sure the men in uniform had those "rations,"

1918: War Department buys the entire output of Bull Durham tobacco. Bull Durham advertises, "When our boys light up, the Huns will light out."  

Never mind that "lighting up" might give away their position and invite enemy bombardment! [Source: Tobacco.org]