I mean, he doesn't have to say it, your comment and the sources did a good job suggesting you only did a cursory read yourself.

1. The first paper states that birds are less sensitive to pyrethroid based pesticides, which makes your broad statements about pesticides sketchy at best.

2. Simple logic doesn't work in science specifically because it's simple and is subject to internal biases. You can't make an assumption and appeal to intuitive reasoning without some evidence to draw that link.

3. Your second paper doesn't back up your claim. It states that bird population loss is a multifaceted problem. Yes, pesticide use is called out as a factor, but so too is habitat loss through urbanisation and unregulated harvesting practices, which kind of answers your point 4.

4. These are all American sources. As a result, very little of this is applicable to the Australian biosphere beyond the most broad strokes since they dont take into account differences in local food webs, urban planning, environmental legislation etc.

TLDR, someone is using irrelevant sources and their dislike of pesticides to justify keeping their cats outside