Lawson's demotion back to the Racing Bulls sister outfit, in a straight swap with Yuki Tsunoda, means Verstappen will have his third teammate in four races in Japan next week.
Verstappen's Dutch compatriot Van der Garde, who raced 19 times for now-defunct Caterham in 2013, said he was "getting a bit tired of" the narrative of having to deliver under pressure or face the consequences.
"Yes, you gotta perform. Yes, the pressure is insane. But in my opinion this comes closer to bullying or a panic move than actual high athlete achievements," he said.
"They made a decision - fully aware - gave Liam two races only to crush his spirit.
"Don't forget the dedication, hard work and success Liam has put in his career so far to achieve the level where he is now... yes, he underperformed the first two races - but if anyone's aware of that it's himself."
Van der Garde urged Lawson to "trust yourself, get your head up, prove them wrong".
Those who liked the post included Verstappen's Instagram account and that of former Red Bull driver Pierre Gasly, who also lost his place alongside the now-four time world champion in 2019.
Dutch media have reported that Verstappen, who has not commented directly, was unhappy with the decision to drop Lawson.