Public use has always been interpreted to include major infrastructure projects—like the pipeline, for example, or earlier, like the transcontinental railroads—even when that infrastructure was privately-owned. What changed in Kelo (and what Trump has supported) was that it can now be used for real estate developments and other private, non-infrastructure projects, as long as those projects are designed to increase tax revenue.
It was the precedent of railroads in the first place that allowed the Kelo decision to be passed. It is defined as the taking of property to transfer to private use that is of public interest:
"In addition to exercising the eminent domain power itself, Congress may delegate it to 'private corporations to be exercised by them in the execution of works in which the public is interested,' such as railroad and utility companies." (Savage, David G., and Joan Biskupic. The Supreme Court and the Powers of the American Government. Washington, D.C.: CQ, 2009. 188.)>
Once that door is opened, there is no reason to stop a city from condemning a blighted area in order to develop it for the public good.
If anything, our current system is much better, since about a hundred years ago the Courts had granted the states the authority to condemn anything, for whatever reason, even without due compensation:
“… the Court had allowed regulations to close down an urban brickyard (1915), to destroy a diseased cedar grove to protect a nearby apple orchard (1928), and to effectively shut down a gravel quarry in a developing suburb (1962)—all without compensation to the owners.â€
http://uculr.com/articles/2012/12/31/the-power-of-eminent-domain-a-history-of-abuse#fn:6
Public use has always been interpreted to include major infrastructure projects—like the pipeline,
That's not true. Like railroads, pipelines have a public utility that must be approved. This determination is not automatic. There is no inherent quality of pipelines that makes them public utilities. They must demonstrate that they will have a benefit for the public:
"Pipeline operators can obtain rights-of-way by entering into leases or voluntary agreements with landowners, or by taking properties through eminent domain proceedings. Interstate pipelines are governed by the Natural Gas Act, which gives the Federal Energy Regulatory Commission the power to issue a certificate of public convenience to operators, who may then condemn property through eminent domain.
This power applies to transmission lines only, not gathering lines. Some, but not all, intrastate pipelines are regulated by the Pennsylvania Public Utility Commission. Some pipeline operators have tried to obtain public utility status with the PUC in order to condemn property to install gathering lines.
A recent decision may signal the end of this trend, as opposition continues to mount against attempts by pipeline operators to style themselves as public utilities to take advantage of special legal rights and powers. Recently, a panel of administrative judges, in Petition of Sunoco Pipeline, Pennsylvania Public Utility Commission Docket No. P-2014- 2411966 (July 23, 2014), recommended that the PUC deny a petition by Sunoco Pipeline L.P. for public utility status, dealing a setback to the industry giant in its attempt to construct its Mariner East pipeline."
http://www.hh-law.com/pipeline-operators-public-utility-or-pipeline-futility/
What changed in Kelo (and what Trump has supported) was that it can now be used for real estate developments and other private, non-infrastructure projects
What changed in Kelo was they simply followed the precedent of other court cases, such as Berman v. Parker (1954), which approved the taking of land, such as "blighted" areas, for redevelopment by any private entity whatsoever:
"Berman v. Parker, 348 U.S. 26 (1954) is a landmark decision of the United States Supreme Court that interpreted the Fifth Amendment's Takings Clause: "nor shall private property be taken for public use, without just compensation" in the Fifth Amendment of the United States Constitution. The court voted 8-0,[1] holding private property could be taken for a public purpose with just compensation. This case laid the foundation for the Court's later important public use cases, Hawaii Housing Authority v. Midkiff, 467 U.S. 229 (1984) and Kelo v. City of New London, 545 U.S. 469 (2005). Critics of recent occurrences of eminent domain uses trace what they view as property rights violations to this case."
... "The key issue addressed was the ability and scope of the government to take and transfer private property to private developers as part of a project to clear blight from an entire area."
https://en.wikipedia.org/wiki/Berman_v._Parker
If you support the Keystone Pipeline, then you support almost a hundred years of Supreme Court precedent that enables the transferring of private property into other private hands.