If they had open minds and really cared they might read some or all of the following works. They could read them all the way through, but if they are lazy (or just don't care about whether they are really right), they can just read the pages listed.
In the 1940s and 50s it was fashionable to cast aspersions on the authenticity of Jesus. By the 60s documents were discovered and scholars began to realize that they had been wrong. Those who have an ax to grind about Jesus choose not to study the more recent investigations, preferring to languish in the inaccuracies of the older ones.
In a 2011 review of the state of modern scholarship, Bart Ehrman (a secular agnostic) wrote: "He certainly existed, as virtually every competent scholar of antiquity, Christian or non-Christian, agrees" B. Ehrman, 2011 Forged : writing in the name of God ISBN 978-0-06-207863-6. page 285
Michael Grant (a classicist) states that "In recent years, 'no serious scholar has ventured to postulate the non historicity of Jesus' or at any rate very few, and they have not succeeded in disposing of the much stronger, indeed very abundant, evidence to the contrary." in Jesus by Michael Grant 2004 ISBN 1898799881 page 200
Richard A. Burridge states: "There are those who argue that Jesus is a figment of the Church’s imagination, that there never was a Jesus at all. I have to say that I do not know any respectable critical scholar who says that any more." in Jesus Now and Then by Richard A. Burridge and Graham Gould (Apr 1, 2004) ISBN 0802809774 page 34
Jesus Remembered by James D. G. Dunn 2003 ISBN 0-8028-3931-2 page 339 states of baptism and crucifixion that these "two facts in the life of Jesus command almost universal assent".
Prophet and Teacher: An Introduction to the Historical Jesus by William R. Herzog (4 Jul 2005) ISBN 0664225284 pages 1-6
Crossan, John Dominic (1995). Jesus: A Revolutionary Biography. HarperOne. p. 145. ISBN 0-06-061662-8. "That he was crucified is as sure as anything historical can ever be, since both Josephus and Tacitus...agree with the Christian accounts on at least that basic fact."
Robert E. Van Voorst Jesus Outside the New Testament: An Introduction to the Ancient Evidence Eerdmans Publishing, 2000. ISBN 0-8028-4368-9 page 16 states: "biblical scholars and classical historians regard theories of non-existence of Jesus as effectively refuted"
James D. G. Dunn "Paul's understanding of the death of Jesus" in Sacrifice and Redemption edited by S. W. Sykes (Dec 3, 2007) Cambridge University Press ISBN 052104460X pages 35-36 states that the theories of non-existence of Jesus are "a thoroughly dead thesis"
The Gospels and Jesus by Graham Stanton, 1989 ISBN 0192132415 Oxford University Press, page 145 states : "Today nearly all historians, whether Christians or not, accept that Jesus existed".
Studying the Historical Jesus: Evaluations of the State of Current Research by Bruce Chilton, Craig A. Evans 1998 ISBN 9004111425 pages 460-470
The Cambridge companion to Jesus by Markus N. A. Bockmuehl 2001 Cambridge Univ Press ISBN 978-0-521-79678-1 pages 123-124. Page 124 state that the "farfetched theories that Jesus' existence was a Christian invention are highly implausible."
Van Voorst, Robert E. (2000). Jesus Outside the New Testament: An Introduction to the Ancient Evidence ISBN 0-8028-4368-9. page 83
Flavius Josephus; Maier, Paul L. (December 1995). Josephus, the essential works: a condensation of Jewish antiquities and The Jewish war ISBN 978-0-8254-3260-6 pages 284-285