Army Ordered 'Psy-Ops' Tactics Used on Members of Congress

And this is different from what lobbyists do daily in the capitol how?

Conducting Psyops on friendly forces is not legal, and it appears as though LTC Holmes made that case to his superiors:

Under duress, Holmes and his team provided Caldwell with background assessments on the visiting senators, and helped prep the general for his high-profile encounters. But according to members of his unit, Holmes did his best to resist the orders. Holmes believed that using his team to target American civilians violated the Smith-Mundt Act of 1948, which was passed by Congress to prevent the State Department from using Soviet-style propaganda techniques on U.S. citizens. But when Holmes brought his concerns to Col. Gregory Breazile, the spokesperson for the Afghan training mission run by Caldwell, the discussion ended in a screaming match. "It's not illegal if I say it isn't!" Holmes recalls Breazile shouting.

It also appears as though LTC Holmes (along with a female major being thrown under the bus with him) may be punished for pushing back:

Three weeks after the exchange, however, Holmes learned that he was the subject of an investigation, called an AR 15-6. The investigation had been ordered by Col. Joe Buche, Caldwell's chief of staff. The 22-page report, obtained by Rolling Stone, reads like something put together by Kenneth Starr.

The Army does influence the public through information, but that is through Public Affairs, not Psyops:

On March 23rd, Holmes emailed the JAG lawyer who handled information operations, saying that the order made him "nervous." The lawyer, Capt. John Scott, agreed with Holmes. "The short answer is that IO doesn’t do that," Scott replied in an email. "[Public affairs] works on the hearts and minds of our own citizens and IO works on the hearts and minds of the citizens of other nations. While the twain do occasionally intersect, such intersections, like violent contact during a soccer game, should be unintentional."