If "coherent" means, "able to form interference patterns," then color filtering and spatial filtering are sufficient to create a "coherent" light source. That's how they used to provide the light for interferometry experiments before lasers* were invented.
It's a fact, established in the early twentieth century, that interferometry works even when you send one photon at a time through the apparatus. There's no requirement for individual photons to be in phase with each other. It's sufficient for each photon to be in phase with itself. https://en.wikipedia.org/wiki/Double-slit_experiment#Interference_from_individual_particles
* The thing that makes lasers so special is that they don't waste any energy (or at least, don't waste much energy) making wavelengths or rays that aren't wanted. When you create coherent light by filtering, the filters throw away almost all of the incident wavelengths and rays. Lots of wasted power, not much coherent light.
Ok, so the physicist, who told me the setup I laid out didn't produce a coherent beam of light, was wrong?
The coherence of a light source isn't just a yes/no quality. It can be quantified.
In the apparatus you described, you can improve the coherence by making the bandpass filter more narrow, and by making the pinhole† smaller, but that means you're throwing away more of the light. A practical version of your apparatus can make light that approaches the coherence of a cheap, multi-mode laser, but the incoherent source lamp must be extremely bright in order to get a useful amount of coherent light out.
I'm guessing that it would be impractical to make such a device that would come anywhere near the coherence that a modern, high-tech, single-mode laser can achieve. So really, whether or not your professor is right or wrong depends somewhat on what you think is good enough to be called "coherent" light.
† In your original question, you said, "two in-line pinholes." But, what you really want for spatial filtering is one pinhole, and one or two lenses. The input lens focuses rays of light that are parallel to the axis of the filter onto the pinhole, while all other rays are blocked. The optional output lens collimates the emerging, spatially coherent rays, into a parallel beam if that's what you need.
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=10768